diff --git a/.github/workflows/workflow.yaml b/.github/workflows/workflow.yaml
index e9319b0641..37d82b5326 100644
--- a/.github/workflows/workflow.yaml
+++ b/.github/workflows/workflow.yaml
@@ -5,7 +5,7 @@ jobs:
   common:
     # TODO - Start using clang-tidy - requires a bit more setup though - http://clang.llvm.org/docs/HowToSetupToolingForLLVM.html
     name: Linting & Formatting
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v2
@@ -19,7 +19,7 @@ jobs:
           ./third-party/run-clang-format/run-clang-format.py -r common decompiler game goalc test --color always
   build-linux:
     name: (Linux) Build & Test
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     defaults:
       run:
         shell: bash
@@ -50,7 +50,7 @@ jobs:
   build-windows:
     # Very good resource - https://cristianadam.eu/20191222/using-github-actions-with-c-plus-plus-and-cmake/
     name: (Windows) Build & Test
-    runs-on: windows-latest
+    runs-on: windows-2019
     defaults:
       run:
         shell: powershell
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 299930c765..43c0cdc3ee 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,3 +1,5 @@
+set(CMAKE_CXX_STANDARD 17)
+
 include("goalc/CMakeLists.txt")
 
 add_executable(goalc-test
diff --git a/test/goalc/framework/test_runner.cpp b/test/goalc/framework/test_runner.cpp
index dd97c3abe3..a9cc841cff 100644
--- a/test/goalc/framework/test_runner.cpp
+++ b/test/goalc/framework/test_runner.cpp
@@ -11,7 +11,7 @@
 #include "goalc/listener/Listener.h"
 #include "goalc/compiler/Compiler.h"
 
-#include "common\util\FileUtil.h"
+#include "common/util/FileUtil.h"
 #include <filesystem>
 
 namespace GoalTest {
diff --git a/test/goalc/framework/test_runner.h b/test/goalc/framework/test_runner.h
index 4358e42a02..4a47954b7e 100644
--- a/test/goalc/framework/test_runner.h
+++ b/test/goalc/framework/test_runner.h
@@ -5,7 +5,6 @@
 
 #include "third-party/inja.hpp"
 #include "goalc/compiler/Compiler.h"
-#include "common\util\FileUtil.h"
 
 namespace GoalTest {
 
diff --git a/test/goalc/test_arithmetic.cpp b/test/goalc/test_arithmetic.cpp
index a423a2693a..6f0014aac4 100644
--- a/test/goalc/test_arithmetic.cpp
+++ b/test/goalc/test_arithmetic.cpp
@@ -10,9 +10,8 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
 
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_collections.cpp b/test/goalc/test_collections.cpp
index ac80aaf318..dc38d944a1 100644
--- a/test/goalc/test_collections.cpp
+++ b/test/goalc/test_collections.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_control_statements.cpp b/test/goalc/test_control_statements.cpp
index 75376b9247..2f920a3f0d 100644
--- a/test/goalc/test_control_statements.cpp
+++ b/test/goalc/test_control_statements.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_float.cpp b/test/goalc/test_float.cpp
index 9770313a3f..24819176ac 100644
--- a/test/goalc/test_float.cpp
+++ b/test/goalc/test_float.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_functions.cpp b/test/goalc/test_functions.cpp
index 2ba12fcad4..eddee8a985 100644
--- a/test/goalc/test_functions.cpp
+++ b/test/goalc/test_functions.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_library.cpp b/test/goalc/test_library.cpp
index b3a9078ca8..045e881b10 100644
--- a/test/goalc/test_library.cpp
+++ b/test/goalc/test_library.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_logic.cpp b/test/goalc/test_logic.cpp
index 0057f7b5e6..326a2f97d1 100644
--- a/test/goalc/test_logic.cpp
+++ b/test/goalc/test_logic.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_loop_recur.cpp b/test/goalc/test_loop_recur.cpp
index cbe9c68f6d..feac01ba33 100644
--- a/test/goalc/test_loop_recur.cpp
+++ b/test/goalc/test_loop_recur.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_macros.cpp b/test/goalc/test_macros.cpp
index ffe0397542..d92ca35f2b 100644
--- a/test/goalc/test_macros.cpp
+++ b/test/goalc/test_macros.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_methods.cpp b/test/goalc/test_methods.cpp
index 92b52faaa8..d3026475f0 100644
--- a/test/goalc/test_methods.cpp
+++ b/test/goalc/test_methods.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_pointers.cpp b/test/goalc/test_pointers.cpp
index a42c753db1..98b75a85f5 100644
--- a/test/goalc/test_pointers.cpp
+++ b/test/goalc/test_pointers.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_strings.cpp b/test/goalc/test_strings.cpp
index fff413a03f..9db9fcab5c 100644
--- a/test/goalc/test_strings.cpp
+++ b/test/goalc/test_strings.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_symbols.cpp b/test/goalc/test_symbols.cpp
index 198804d614..196121881d 100644
--- a/test/goalc/test_symbols.cpp
+++ b/test/goalc/test_symbols.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_variables.cpp b/test/goalc/test_variables.cpp
index 6c6d093377..6caa32202a 100644
--- a/test/goalc/test_variables.cpp
+++ b/test/goalc/test_variables.cpp
@@ -8,9 +8,7 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/test/goalc/test_with_game.cpp b/test/goalc/test_with_game.cpp
index 3daf11b176..94dc1ad3b2 100644
--- a/test/goalc/test_with_game.cpp
+++ b/test/goalc/test_with_game.cpp
@@ -8,9 +8,8 @@
 
 #include "third-party/inja.hpp"
 #include "third-party/json.hpp"
-#include <common\util\FileUtil.h>
-
-#include <test\goalc\framework\test_runner.h>
+#include "common/util/FileUtil.h"
+#include <test/goalc/framework/test_runner.h>
 
 #include <iostream>
 #include <string>
diff --git a/third-party/inja.hpp b/third-party/inja.hpp
index b286ce0264..c32b5ca75e 100644
--- a/third-party/inja.hpp
+++ b/third-party/inja.hpp
@@ -1,10 +1,8 @@
-// Copyright (c) 2019 Pantor. All rights reserved.
+// Copyright (c) 2020 Pantor. All rights reserved.
 
 #ifndef INCLUDE_INJA_INJA_HPP_
 #define INCLUDE_INJA_INJA_HPP_
 
-#include <iostream>
-
 #include <third-party/json.hpp>
 
 // #include "environment.hpp"
@@ -14,6 +12,7 @@
 #define INCLUDE_INJA_ENVIRONMENT_HPP_
 
 #include <fstream>
+#include <iostream>
 #include <memory>
 #include <sstream>
 #include <string>
@@ -1461,7 +1460,9 @@ struct LexerConfig {
   std::string statement_close_force_rstrip {"-%}"};
   std::string line_statement {"##"};
   std::string expression_open {"{{"};
+  std::string expression_open_force_lstrip {"{{-"};
   std::string expression_close {"}}"};
+  std::string expression_close_force_rstrip {"-}}"};
   std::string comment_open {"{#"};
   std::string comment_close {"#}"};
   std::string open_chars {"#{"};
@@ -1486,6 +1487,9 @@ struct LexerConfig {
     if (open_chars.find(expression_open[0]) == std::string::npos) {
       open_chars += expression_open[0];
     }
+    if (open_chars.find(expression_open_force_lstrip[0]) == std::string::npos) {
+      open_chars += expression_open_force_lstrip[0];
+    }
     if (open_chars.find(comment_open[0]) == std::string::npos) {
       open_chars += comment_open[0];
     }
@@ -1527,6 +1531,7 @@ using json = nlohmann::json;
 
 using Arguments = std::vector<const json *>;
 using CallbackFunction = std::function<json(Arguments &args)>;
+using VoidCallbackFunction = std::function<void(Arguments &args)>;
 
 /*!
  * \brief Class for builtin functions and user-defined callbacks.
@@ -1583,14 +1588,15 @@ public:
     None,
   };
 
-  const int VARIADIC {-1};
-
   struct FunctionData {
-    Operation operation;
-
-    CallbackFunction callback;
+    explicit FunctionData(const Operation &op, const CallbackFunction &cb = CallbackFunction{}) : operation(op), callback(cb) {}
+    const Operation operation;
+    const CallbackFunction callback;
   };
 
+private:
+  const int VARIADIC {-1};
+
   std::map<std::pair<std::string, int>, FunctionData> function_storage = {
     {std::make_pair("at", 2), FunctionData { Operation::At }},
     {std::make_pair("default", 2), FunctionData { Operation::Default }},
@@ -1642,7 +1648,7 @@ public:
       }
     }
 
-    return { Operation::None };
+    return FunctionData { Operation::None };
   }
 };
 
@@ -1682,39 +1688,35 @@ struct SourceLocation {
 };
 
 struct InjaError : public std::runtime_error {
-  std::string type;
-  std::string message;
+  const std::string type;
+  const std::string message;
 
-  bool has_location {false};
-  SourceLocation location;
+  const SourceLocation location;
 
-  InjaError(const std::string &type, const std::string &message)
-      : std::runtime_error("[inja.exception." + type + "] " + message), type(type), message(message) {}
+  explicit InjaError(const std::string &type, const std::string &message)
+      : std::runtime_error("[inja.exception." + type + "] " + message), type(type), message(message), location({0, 0}) {}
 
-  InjaError(const std::string &type, const std::string &message, SourceLocation location)
+  explicit InjaError(const std::string &type, const std::string &message, SourceLocation location)
       : std::runtime_error("[inja.exception." + type + "] (at " + std::to_string(location.line) + ":" +
                            std::to_string(location.column) + ") " + message),
-        type(type), message(message), has_location(true), location(location) {}
+        type(type), message(message), location(location) {}
 };
 
 struct ParserError : public InjaError {
-  ParserError(const std::string &message) : InjaError("parser_error", message) {}
-  ParserError(const std::string &message, SourceLocation location) : InjaError("parser_error", message, location) {}
+  explicit ParserError(const std::string &message, SourceLocation location) : InjaError("parser_error", message, location) {}
 };
 
 struct RenderError : public InjaError {
-  RenderError(const std::string &message) : InjaError("render_error", message) {}
-  RenderError(const std::string &message, SourceLocation location) : InjaError("render_error", message, location) {}
+  explicit RenderError(const std::string &message, SourceLocation location) : InjaError("render_error", message, location) {}
 };
 
 struct FileError : public InjaError {
-  FileError(const std::string &message) : InjaError("file_error", message) {}
-  FileError(const std::string &message, SourceLocation location) : InjaError("file_error", message, location) {}
+  explicit FileError(const std::string &message) : InjaError("file_error", message) {}
+  explicit FileError(const std::string &message, SourceLocation location) : InjaError("file_error", message, location) {}
 };
 
 struct JsonError : public InjaError {
-  JsonError(const std::string &message) : InjaError("json_error", message) {}
-  JsonError(const std::string &message, SourceLocation location) : InjaError("json_error", message, location) {}
+  explicit JsonError(const std::string &message, SourceLocation location) : InjaError("json_error", message, location) {}
 };
 
 } // namespace inja
@@ -1874,7 +1876,7 @@ inline SourceLocation get_source_location(nonstd::string_view content, size_t po
   size_t search_start = 0;
   while (search_start <= sliced.size()) {
     search_start = sliced.find("\n", search_start) + 1;
-    if (search_start <= 0) {
+    if (search_start == 0) {
       break;
     }
     count_lines += 1;
@@ -1897,6 +1899,7 @@ class Lexer {
   enum class State {
     Text,
     ExpressionStart,
+    ExpressionStartForceLstrip,
     ExpressionBody,
     LineStart,
     LineBody,
@@ -2146,7 +2149,7 @@ class Lexer {
   }
 
 public:
-  explicit Lexer(const LexerConfig &config) : config(config) {}
+  explicit Lexer(const LexerConfig &config) : config(config), state(State::Text), minus_state(MinusState::Number) {}
 
   SourceLocation current_position() const {
     return get_source_location(m_in, tok_start);
@@ -2158,6 +2161,11 @@ public:
     pos = 0;
     state = State::Text;
     minus_state = MinusState::Number;
+
+    // Consume byte order mark (BOM) for UTF-8
+    if (inja::string_view::starts_with(m_in, "\xEF\xBB\xBF")) {
+      m_in = m_in.substr(3);
+    }
   }
 
   Token scan() {
@@ -2184,7 +2192,12 @@ public:
       nonstd::string_view open_str = m_in.substr(pos);
       bool must_lstrip = false;
       if (inja::string_view::starts_with(open_str, config.expression_open)) {
-        state = State::ExpressionStart;
+        if (inja::string_view::starts_with(open_str, config.expression_open_force_lstrip)) {
+          state = State::ExpressionStartForceLstrip;
+          must_lstrip = true;
+        } else {
+          state = State::ExpressionStart;
+        }
       } else if (inja::string_view::starts_with(open_str, config.statement_open)) {
         if (inja::string_view::starts_with(open_str, config.statement_open_no_lstrip)) {
           state = State::StatementStartNoLstrip;
@@ -2198,8 +2211,7 @@ public:
       } else if (inja::string_view::starts_with(open_str, config.comment_open)) {
         state = State::CommentStart;
         must_lstrip = config.lstrip_blocks;
-      } else if ((pos == 0 || m_in[pos - 1] == '\n') &&
-                 inja::string_view::starts_with(open_str, config.line_statement)) {
+      } else if ((pos == 0 || m_in[pos - 1] == '\n') && inja::string_view::starts_with(open_str, config.line_statement)) {
         state = State::LineStart;
       } else {
         pos += 1; // wasn't actually an opening sequence
@@ -2221,6 +2233,11 @@ public:
       pos += config.expression_open.size();
       return make_token(Token::Kind::ExpressionOpen);
     }
+    case State::ExpressionStartForceLstrip: {
+      state = State::ExpressionBody;
+      pos += config.expression_open_force_lstrip.size();
+      return make_token(Token::Kind::ExpressionOpen);
+    }
     case State::LineStart: {
       state = State::LineBody;
       pos += config.line_statement.size();
@@ -2247,7 +2264,7 @@ public:
       return make_token(Token::Kind::CommentOpen);
     }
     case State::ExpressionBody:
-      return scan_body(config.expression_close, Token::Kind::ExpressionClose);
+      return scan_body(config.expression_close, Token::Kind::ExpressionClose, config.expression_close_force_rstrip);
     case State::LineBody:
       return scan_body("\n", Token::Kind::LineStatementClose);
     case State::StatementBody:
@@ -2313,6 +2330,7 @@ class ForArrayStatementNode;
 class ForObjectStatementNode;
 class IfStatementNode;
 class IncludeStatementNode;
+class SetStatementNode;
 
 
 class NodeVisitor {
@@ -2330,6 +2348,7 @@ public:
   virtual void visit(const ForObjectStatementNode& node) = 0;
   virtual void visit(const IfStatementNode& node) = 0;
   virtual void visit(const IncludeStatementNode& node) = 0;
+  virtual void visit(const SetStatementNode& node) = 0;
 };
 
 /*!
@@ -2359,7 +2378,7 @@ public:
 
 class TextNode : public AstNode {
 public:
-  size_t length;
+  const size_t length;
 
   explicit TextNode(size_t pos, size_t length): AstNode(pos), length(length) { }
 
@@ -2379,7 +2398,7 @@ public:
 
 class LiteralNode : public ExpressionNode {
 public:
-  nlohmann::json value;
+  const nlohmann::json value;
 
   explicit LiteralNode(const nlohmann::json& value, size_t pos) : ExpressionNode(pos), value(value) { }
 
@@ -2390,8 +2409,8 @@ public:
 
 class JsonNode : public ExpressionNode {
 public:
-  std::string name;
-  std::string ptr {""};
+  const std::string name;
+  const json::json_pointer ptr;
 
   static std::string convert_dot_to_json_ptr(nonstd::string_view ptr_name) {
     std::string result;
@@ -2404,9 +2423,7 @@ public:
     return result;
   }
 
-  explicit JsonNode(nonstd::string_view ptr_name, size_t pos) : ExpressionNode(pos), name(ptr_name) {
-    ptr = convert_dot_to_json_ptr(ptr_name);
-  }
+  explicit JsonNode(nonstd::string_view ptr_name, size_t pos) : ExpressionNode(pos), name(ptr_name), ptr(json::json_pointer(convert_dot_to_json_ptr(ptr_name))) { }
 
   void accept(NodeVisitor& v) const {
     v.visit(*this);
@@ -2537,18 +2554,18 @@ class ForStatementNode : public StatementNode {
 public:
   ExpressionListNode condition;
   BlockNode body;
-  BlockNode *parent;
+  BlockNode *const parent;
 
-  ForStatementNode(size_t pos) : StatementNode(pos) { }
+  ForStatementNode(BlockNode *const parent, size_t pos) : StatementNode(pos), parent(parent) { }
 
   virtual void accept(NodeVisitor& v) const = 0;
 };
 
 class ForArrayStatementNode : public ForStatementNode {
 public:
-  nonstd::string_view value;
+  const std::string value;
 
-  explicit ForArrayStatementNode(nonstd::string_view value, size_t pos) : ForStatementNode(pos), value(value) { }
+  explicit ForArrayStatementNode(const std::string& value, BlockNode *const parent, size_t pos) : ForStatementNode(parent, pos), value(value) { }
 
   void accept(NodeVisitor& v) const {
     v.visit(*this);
@@ -2557,10 +2574,10 @@ public:
 
 class ForObjectStatementNode : public ForStatementNode {
 public:
-  nonstd::string_view key;
-  nonstd::string_view value;
+  const std::string key;
+  const std::string value;
 
-  explicit ForObjectStatementNode(nonstd::string_view key, nonstd::string_view value, size_t pos) : ForStatementNode(pos), key(key), value(value) { }
+  explicit ForObjectStatementNode(const std::string& key, const std::string& value, BlockNode *const parent, size_t pos) : ForStatementNode(parent, pos), key(key), value(value) { }
 
   void accept(NodeVisitor& v) const {
     v.visit(*this);
@@ -2572,13 +2589,13 @@ public:
   ExpressionListNode condition;
   BlockNode true_statement;
   BlockNode false_statement;
-  BlockNode *parent;
+  BlockNode *const parent;
 
-  bool is_nested;
+  const bool is_nested;
   bool has_false_statement {false};
 
-  explicit IfStatementNode(size_t pos) : StatementNode(pos), is_nested(false) { }
-  explicit IfStatementNode(bool is_nested, size_t pos) : StatementNode(pos), is_nested(is_nested) { }
+  explicit IfStatementNode(BlockNode *const parent, size_t pos) : StatementNode(pos), parent(parent), is_nested(false) { }
+  explicit IfStatementNode(bool is_nested, BlockNode *const parent, size_t pos) : StatementNode(pos), parent(parent), is_nested(is_nested) { }
 
   void accept(NodeVisitor& v) const {
     v.visit(*this);
@@ -2587,7 +2604,7 @@ public:
 
 class IncludeStatementNode : public StatementNode {
 public:
-  std::string file;
+  const std::string file;
 
   explicit IncludeStatementNode(const std::string& file, size_t pos) : StatementNode(pos), file(file) { }
 
@@ -2596,6 +2613,18 @@ public:
   };
 };
 
+class SetStatementNode : public StatementNode {
+public:
+  const std::string key;
+  ExpressionListNode expression;
+
+  explicit SetStatementNode(const std::string& key, size_t pos) : StatementNode(pos), key(key) { }
+
+  void accept(NodeVisitor& v) const {
+    v.visit(*this);
+  };
+};
+
 } // namespace inja
 
 #endif // INCLUDE_INJA_NODE_HPP_
@@ -2672,6 +2701,8 @@ class StatisticsVisitor : public NodeVisitor {
 
   void visit(const IncludeStatementNode&) { }
 
+  void visit(const SetStatementNode&) { }
+
 public:
   unsigned int variable_counter;
 
@@ -2835,14 +2866,14 @@ class Parser {
             add_json_literal(tmpl.content.c_str());
           }
 
+	      // Operator
+        } else if (tok.text == "and" || tok.text == "or" || tok.text == "in" || tok.text == "not") {
+          goto parse_operator;
+
         // Functions
         } else if (peek_tok.kind == Token::Kind::LeftParen) {
           operator_stack.emplace(std::make_shared<FunctionNode>(static_cast<std::string>(tok.text), tok.text.data() - tmpl.content.c_str()));
-          function_stack.emplace(operator_stack.top().get(), current_paren_level);
-
-        // Operator
-        } else if (tok.text == "and" || tok.text == "or" || tok.text == "in" || tok.text == "not") {
-          goto parse_operator;
+          function_stack.emplace(operator_stack.top().get(), current_paren_level);       
 
         // Variables
         } else {
@@ -2964,12 +2995,12 @@ class Parser {
       } break;
       case Token::Kind::RightParen: {
         current_paren_level -= 1;
-        while (operator_stack.top()->operation != FunctionStorage::Operation::ParenLeft) {
+        while (!operator_stack.empty() && operator_stack.top()->operation != FunctionStorage::Operation::ParenLeft) {
           current_expression_list->rpn_output.emplace_back(operator_stack.top());
           operator_stack.pop();
         }
 
-        if (operator_stack.top()->operation == FunctionStorage::Operation::ParenLeft) {
+        if (!operator_stack.empty() && operator_stack.top()->operation == FunctionStorage::Operation::ParenLeft) {
           operator_stack.pop();
         }
 
@@ -2984,6 +3015,12 @@ class Parser {
             func->callback = function_data.callback;
           }
 
+          if (operator_stack.empty()) {
+            throw_parser_error("internal error at function " + func->name);
+          }
+
+          current_expression_list->rpn_output.emplace_back(operator_stack.top());
+          operator_stack.pop();
           function_stack.pop();
         }
       }
@@ -3010,9 +3047,8 @@ class Parser {
     if (tok.text == static_cast<decltype(tok.text)>("if")) {
       get_next_token();
 
-      auto if_statement_node = std::make_shared<IfStatementNode>(tok.text.data() - tmpl.content.c_str());
+      auto if_statement_node = std::make_shared<IfStatementNode>(current_block, tok.text.data() - tmpl.content.c_str());
       current_block->nodes.emplace_back(if_statement_node);
-      if_statement_node->parent = current_block;
       if_statement_stack.emplace(if_statement_node.get());
       current_block = &if_statement_node->true_statement;
       current_expression_list = &if_statement_node->condition;
@@ -3035,9 +3071,8 @@ class Parser {
       if (tok.kind == Token::Kind::Id && tok.text == static_cast<decltype(tok.text)>("if")) {
         get_next_token();
 
-        auto if_statement_node = std::make_shared<IfStatementNode>(true, tok.text.data() - tmpl.content.c_str());
+        auto if_statement_node = std::make_shared<IfStatementNode>(true, current_block, tok.text.data() - tmpl.content.c_str());
         current_block->nodes.emplace_back(if_statement_node);
-        if_statement_node->parent = current_block;
         if_statement_stack.emplace(if_statement_node.get());
         current_block = &if_statement_node->true_statement;
         current_expression_list = &if_statement_node->condition;
@@ -3086,15 +3121,14 @@ class Parser {
         value_token = tok;
         get_next_token();
 
-        for_statement_node = std::make_shared<ForObjectStatementNode>(key_token.text, value_token.text, tok.text.data() - tmpl.content.c_str());
+        for_statement_node = std::make_shared<ForObjectStatementNode>(static_cast<std::string>(key_token.text), static_cast<std::string>(value_token.text), current_block, tok.text.data() - tmpl.content.c_str());
 
       // Array type
       } else {
-        for_statement_node = std::make_shared<ForArrayStatementNode>(value_token.text, tok.text.data() - tmpl.content.c_str());
+        for_statement_node = std::make_shared<ForArrayStatementNode>(static_cast<std::string>(value_token.text), current_block, tok.text.data() - tmpl.content.c_str());
       }
 
       current_block->nodes.emplace_back(for_statement_node);
-      for_statement_node->parent = current_block;
       for_statement_stack.emplace(for_statement_node.get());
       current_block = &for_statement_node->body;
       current_expression_list = &for_statement_node->condition;
@@ -3145,6 +3179,29 @@ class Parser {
 
       get_next_token();
 
+    } else if (tok.text == static_cast<decltype(tok.text)>("set")) {
+      get_next_token();
+
+      if (tok.kind != Token::Kind::Id) {
+        throw_parser_error("expected variable name, got '" + tok.describe() + "'");
+      }
+
+      std::string key = static_cast<std::string>(tok.text);
+      get_next_token();
+
+      auto set_statement_node = std::make_shared<SetStatementNode>(key, tok.text.data() - tmpl.content.c_str());
+      current_block->nodes.emplace_back(set_statement_node);
+      current_expression_list = &set_statement_node->expression;
+
+      if (tok.text != static_cast<decltype(tok.text)>("=")) {
+        throw_parser_error("expected '=', got '" + tok.describe() + "'");
+      }
+      get_next_token();
+
+      if (!parse_expression(tmpl, closing)) {
+        return false;
+      }
+
     } else {
       return false;
     }
@@ -3292,32 +3349,30 @@ class Renderer : public NodeVisitor  {
   const json *json_input;
   std::ostream *output_stream;
 
-  json json_loop_data;
-  json* current_loop_data = &json_loop_data["loop"];
+  json json_additional_data;
+  json* current_loop_data = &json_additional_data["loop"];
 
   std::vector<std::shared_ptr<json>> json_tmp_stack;
   std::stack<const json*> json_eval_stack;
   std::stack<const JsonNode*> not_found_stack;
 
   bool truthy(const json* data) const {
-    if (data->empty()) {
-      return false;
+    if (data->is_boolean()) {
+      return data->get<bool>();
     } else if (data->is_number()) {
       return (*data != 0);
-    } else if (data->is_string()) {
-      return !data->empty();
-    }
-
-    try {
-      return data->get<bool>();
-    } catch (json::type_error &e) {
-      throw JsonError(e.what());
+    } else if (data->is_null()) {
+      return false;
     }
+    return !data->empty();
   }
 
-  void print_json(const json* value) {
+  void print_json(const std::shared_ptr<json> value) {
     if (value->is_string()) {
-      *output_stream << value->get_ref<const std::string &>();
+      *output_stream << value->get_ref<const json::string_t&>();
+    } else if (value->is_number_integer()) {
+      *output_stream << value->get<const json::number_integer_t>();
+    } else if (value->is_null()) {
     } else {
       *output_stream << value->dump();
     }
@@ -3330,9 +3385,7 @@ class Renderer : public NodeVisitor  {
 
     if (json_eval_stack.empty()) {
       throw_renderer_error("empty expression", expression_list);
-    }
-
-    if (json_eval_stack.size() != 1) {
+    } else if (json_eval_stack.size() != 1) {
       throw_renderer_error("malformed expression", expression_list);
     }
 
@@ -3416,17 +3469,13 @@ class Renderer : public NodeVisitor  {
   }
 
   void visit(const JsonNode& node) {
-    auto ptr = json::json_pointer(node.ptr);
-
-    try {
-      // First try to evaluate as a loop variable
-      if (json_loop_data.contains(ptr)) {
-        json_eval_stack.push(&json_loop_data.at(ptr));
-      } else {
-        json_eval_stack.push(&json_input->at(ptr));
-      }
-
-    } catch (std::exception &) {
+    if (json_additional_data.contains(node.ptr)) {
+      json_eval_stack.push(&(json_additional_data[node.ptr]));
+    
+    } else if (json_input->contains(node.ptr)) {
+      json_eval_stack.push(&(*json_input)[node.ptr]);
+    
+    } else {
       // Try to evaluate as a no-argument callback
       auto function_data = function_storage.find_function(node.name, 0);
       if (function_data.operation == FunctionStorage::Operation::Callback) {
@@ -3509,7 +3558,7 @@ class Renderer : public NodeVisitor  {
     case Op::Add: {
       auto args = get_arguments<2>(node);
       if (args[0]->is_string() && args[1]->is_string()) {
-        result_ptr = std::make_shared<json>(args[0]->get<std::string>() + args[1]->get<std::string>());
+        result_ptr = std::make_shared<json>(args[0]->get_ref<const std::string&>() + args[1]->get_ref<const std::string&>());
         json_tmp_stack.push_back(result_ptr);
       } else if (args[0]->is_number_integer() && args[1]->is_number_integer()) {
         result_ptr = std::make_shared<json>(args[0]->get<int>() + args[1]->get<int>());
@@ -3741,7 +3790,7 @@ class Renderer : public NodeVisitor  {
   }
 
   void visit(const ExpressionListNode& node) {
-    print_json(eval_expression_list(node).get());
+    print_json(eval_expression_list(node));
   }
 
   void visit(const StatementNode&) { }
@@ -3759,24 +3808,31 @@ class Renderer : public NodeVisitor  {
       (*current_loop_data)["parent"] = std::move(tmp);
     }
 
+    size_t index = 0;
+    (*current_loop_data)["is_first"] = true;
+    (*current_loop_data)["is_last"] = (result->size() <= 1);
     for (auto it = result->begin(); it != result->end(); ++it) {
-      json_loop_data[static_cast<std::string>(node.value)] = *it;
+      json_additional_data[static_cast<std::string>(node.value)] = *it;
 
-      size_t index = std::distance(result->begin(), it);
       (*current_loop_data)["index"] = index;
       (*current_loop_data)["index1"] = index + 1;
-      (*current_loop_data)["is_first"] = (index == 0);
-      (*current_loop_data)["is_last"] = (index == result->size() - 1);
+      if (index == 1) {
+        (*current_loop_data)["is_first"] = false;
+      }
+      if (index == result->size() - 1) {
+        (*current_loop_data)["is_last"] = true;
+      }
 
       node.body.accept(*this);
+      ++index;
     }
 
-    json_loop_data[static_cast<std::string>(node.value)].clear();
+    json_additional_data[static_cast<std::string>(node.value)].clear();
     if (!(*current_loop_data)["parent"].empty()) {
       auto tmp = (*current_loop_data)["parent"];
       *current_loop_data = std::move(tmp);
     } else {
-      current_loop_data = &json_loop_data["loop"];
+      current_loop_data = &json_additional_data["loop"];
     }
   }
 
@@ -3790,25 +3846,32 @@ class Renderer : public NodeVisitor  {
       (*current_loop_data)["parent"] = std::move(*current_loop_data);
     }
 
+    size_t index = 0;
+    (*current_loop_data)["is_first"] = true;
+    (*current_loop_data)["is_last"] = (result->size() <= 1);
     for (auto it = result->begin(); it != result->end(); ++it) {
-      json_loop_data[static_cast<std::string>(node.key)] = it.key();
-      json_loop_data[static_cast<std::string>(node.value)] = it.value();
+      json_additional_data[static_cast<std::string>(node.key)] = it.key();
+      json_additional_data[static_cast<std::string>(node.value)] = it.value();
 
-      size_t index = std::distance(result->begin(), it);
       (*current_loop_data)["index"] = index;
       (*current_loop_data)["index1"] = index + 1;
-      (*current_loop_data)["is_first"] = (index == 0);
-      (*current_loop_data)["is_last"] = (index == result->size() - 1);
+      if (index == 1) {
+        (*current_loop_data)["is_first"] = false;
+      }
+      if (index == result->size() - 1) {
+        (*current_loop_data)["is_last"] = true;
+      }
 
       node.body.accept(*this);
+      ++index;
     }
 
-    json_loop_data[static_cast<std::string>(node.key)].clear();
-    json_loop_data[static_cast<std::string>(node.value)].clear();
+    json_additional_data[static_cast<std::string>(node.key)].clear();
+    json_additional_data[static_cast<std::string>(node.value)].clear();
     if (!(*current_loop_data)["parent"].empty()) {
       *current_loop_data = std::move((*current_loop_data)["parent"]);
     } else {
-      current_loop_data = &json_loop_data["loop"];
+      current_loop_data = &json_additional_data["loop"];
     }
   }
 
@@ -3826,12 +3889,16 @@ class Renderer : public NodeVisitor  {
     auto included_template_it = template_storage.find(node.file);
 
     if (included_template_it != template_storage.end()) {
-      sub_renderer.render_to(*output_stream, included_template_it->second, *json_input, &json_loop_data);
+      sub_renderer.render_to(*output_stream, included_template_it->second, *json_input, &json_additional_data);
     } else if (config.throw_at_missing_includes) {
       throw_renderer_error("include '" + node.file + "' not found", node);
     }
   }
 
+  void visit(const SetStatementNode& node) {
+    json_additional_data[node.key] = *eval_expression_list(node.expression);
+  }
+
 public:
   Renderer(const RenderConfig& config, const TemplateStorage &template_storage, const FunctionStorage &function_storage)
       : config(config), template_storage(template_storage), function_storage(function_storage) { }
@@ -3841,7 +3908,8 @@ public:
     current_template = &tmpl;
     json_input = &data;
     if (loop_data) {
-      json_loop_data = *loop_data;
+      json_additional_data = *loop_data;
+      current_loop_data = &json_additional_data["loop"];
     }
 
     current_template->root.accept(*this);
@@ -3906,7 +3974,9 @@ public:
   /// Sets the opener and closer for template expressions
   void set_expression(const std::string &open, const std::string &close) {
     lexer_config.expression_open = open;
+    lexer_config.expression_open_force_lstrip = open + "-";
     lexer_config.expression_close = close;
+    lexer_config.expression_close_force_rstrip = "-" + close;
     lexer_config.update_open_chars();
   }
 
@@ -4015,7 +4085,14 @@ public:
   @brief Adds a variadic callback
   */
   void add_callback(const std::string &name, const CallbackFunction &callback) {
-    function_storage.add_callback(name, -1, callback);
+    add_callback(name, -1, callback);
+  }
+
+  /*!
+  @brief Adds a variadic void callback
+  */
+  void add_void_callback(const std::string &name, const VoidCallbackFunction &callback) {
+    add_void_callback(name, -1, callback);
   }
 
   /*!
@@ -4025,6 +4102,13 @@ public:
     function_storage.add_callback(name, num_args, callback);
   }
 
+  /*!
+  @brief Adds a void callback with given number or arguments
+  */
+  void add_void_callback(const std::string &name, int num_args, const VoidCallbackFunction &callback) {
+    function_storage.add_callback(name, num_args, [callback](Arguments& args) { callback(args); return json(); });
+  }
+
   /** Includes a template with a given name into the environment.
    * Then, a template can be rendered in another template using the
    * include "<name>" syntax.