diff --git a/boot/ast.cc b/boot/ast.cc
index efaaad1..ad25adb 100644
--- a/boot/ast.cc
+++ b/boot/ast.cc
@@ -795,7 +795,7 @@ namespace elna::boot
     }
 
     return_statement::return_statement(const struct position position, expression *return_expression)
-        : node(position), return_expression(return_expression)
+        : node(position), m_return_expression(return_expression)
     {
     }
 
@@ -804,9 +804,14 @@ namespace elna::boot
         visitor->visit(this);
     }
 
+    expression& return_statement::return_expression()
+    {
+        return *m_return_expression;
+    }
+
     return_statement::~return_statement()
     {
-        delete this->return_expression;
+        delete m_return_expression;
     }
 
     case_statement::case_statement(const struct position position,
@@ -914,13 +919,6 @@ namespace elna::boot
     {
     }
 
-    while_statement::while_statement(const struct position position, conditional_statements *body,
-            std::vector<conditional_statements *>&& branches, const std::string& label,
-            std::vector<statement *> *alternative)
-        : node(position), m_body(body), branches(std::move(branches)), label(label), alternative(alternative)
-    {
-    }
-
     void while_statement::accept(parser_visitor *visitor)
     {
         visitor->visit(this);
diff --git a/boot/parser.yy b/boot/parser.yy
index e82a421..575d752 100644
--- a/boot/parser.yy
+++ b/boot/parser.yy
@@ -145,10 +145,9 @@ along with GCC; see the file COPYING3.  If not see
 %type <std::vector<elna::boot::expression *>> expressions actual_parameter_list;
 %type <elna::boot::designator_expression *> designator_expression;
 %type <elna::boot::procedure_call*> call_expression;
-%type <elna::boot::while_statement *> while_statement;
 %type <elna::boot::return_statement *> return_statement;
 %type <elna::boot::statement *> statement;
-%type <std::vector<elna::boot::statement *>> statements;
+%type <std::vector<elna::boot::statement *>> required_statements optional_statements statement_part;
 %type <elna::boot::procedure_definition *> procedure_definition;
 %type <std::pair<std::vector<std::string>, elna::boot::procedure_type_expression *>> procedure_heading;
 %type <elna::boot::procedure_type_expression::return_t> return_declaration;
@@ -158,7 +157,7 @@ along with GCC; see the file COPYING3.  If not see
 %type <std::unique_ptr<elna::boot::block>> block;
 %type <elna::boot::field_declaration> field_declaration formal_parameter;
 %type <std::vector<std::pair<std::string, elna::boot::type_expression *>>>
-    optional_fields required_fields formal_parameters;
+    optional_fields required_fields formal_parameters formal_parameter_list;
 %type <std::vector<elna::boot::conditional_statements *>> elsif_then_statements elsif_do_statements;
 %type <std::vector<elna::boot::statement *> *> else_statements;
 %type <elna::boot::cast_expression *> cast_expression;
@@ -168,7 +167,7 @@ along with GCC; see the file COPYING3.  If not see
 %type <std::vector<elna::boot::import_declaration *>> import_declarations import_part;
 %%
 program:
-    "program" import_part constant_part type_part variable_part procedure_part "begin" statements "end" "."
+    "program" import_part constant_part type_part variable_part procedure_part "begin" optional_statements "end" "."
         {
             auto tree = new boot::program(boot::make_position(@7));
 
@@ -193,9 +192,18 @@ program:
 
             driver.tree.reset(tree);
         }
-block: constant_part variable_part "begin" statements "end"
+block: constant_part variable_part statement_part "end"
         {
-            $$ = std::make_unique<boot::block>(std::move($1), std::move($2), std::move($4));
+            $$ = std::make_unique<boot::block>(std::move($1), std::move($2), std::move($3));
+        }
+statement_part:
+    /* no statements */ {}
+    | "begin" required_statements { std::swap($$, $2); }
+    | return_statement { $$.push_back($1); }
+    | "begin" required_statements ";" return_statement
+        {
+            std::swap($$, $2);
+            $$.push_back($4);
         }
 identifier_definition:
     IDENTIFIER "*" { $$ = boot::identifier_definition{ $1, true }; }
@@ -211,11 +219,10 @@ return_declaration:
     /* proper procedure */ {}
     | "->" "!" { $$ = boot::procedure_type_expression::return_t(std::monostate{}); }
     | "->" type_expression { $$ = boot::procedure_type_expression::return_t($2); }
-procedure_heading:
-    "(" formal_parameters ")" return_declaration
+procedure_heading: formal_parameter_list return_declaration
         {
-            $$.second = new boot::procedure_type_expression(boot::make_position(@1), std::move($4));
-            for (auto& [name, type] : $2)
+            $$.second = new boot::procedure_type_expression(boot::make_position(@1), std::move($2));
+            for (auto& [name, type] : $1)
             {
                 $$.first.emplace_back(std::move(name));
                 $$.second->parameters.push_back(type);
@@ -250,7 +257,7 @@ call_expression: designator_expression actual_parameter_list
 cast_expression: "cast" "(" expression ":" type_expression ")"
         { $$ = new boot::cast_expression(boot::make_position(@1), $5, $3); }
 elsif_do_statements:
-    "elsif" expression "do" statements elsif_do_statements
+    "elsif" expression "do" optional_statements elsif_do_statements
         {
             boot::conditional_statements *branch = new boot::conditional_statements($2, std::move($4));
             std::swap($5, $$);
@@ -258,36 +265,18 @@ elsif_do_statements:
         }
     | {}
 else_statements:
-    "else" statements { $$ = new std::vector<boot::statement *>(std::move($2)); }
+    "else" optional_statements { $$ = new std::vector<boot::statement *>(std::move($2)); }
     | { $$ = nullptr; }
-while_statement:
-    "while" expression "do" statements elsif_do_statements else_statements "end"
-        {
-            boot::conditional_statements *body = new boot::conditional_statements($2, std::move($4));
-            $$ = new boot::while_statement(boot::make_position(@1), body, std::move($5), $6);
-        }
-    | "while" expression "," IDENTIFIER "do" statements elsif_do_statements else_statements "end"
-        {
-            boot::conditional_statements *body = new boot::conditional_statements($2, std::move($6));
-            $$ = new boot::while_statement(boot::make_position(@1), body, std::move($7), $4, $8);
-        }
 elsif_then_statements:
-    "elsif" expression "then" statements elsif_then_statements
+    "elsif" expression "then" optional_statements elsif_then_statements
         {
             boot::conditional_statements *branch = new boot::conditional_statements($2, std::move($4));
             std::swap($5, $$);
             $$.emplace($$.begin(), branch);
         }
     | {}
-return_statement:
-    "return" expression
-        {
-            $$ = new boot::return_statement(boot::make_position(@1), $2);
-        }
-    | "return"
-        {
-            $$ = new boot::return_statement(boot::make_position(@1));
-        }
+return_statement: "return" expression
+        { $$ = new boot::return_statement(boot::make_position(@1), $2); }
 literal:
     INTEGER { $$ = new boot::literal<std::int32_t>(boot::make_position(@1), $1); }
     | WORD { $$ = new boot::literal<std::uint32_t>(boot::make_position(@1), $1); }
@@ -421,18 +410,23 @@ designator_expression:
 statement:
     designator_expression ":=" expression
         { $$ = new boot::assign_statement(boot::make_position(@1), $1, $3); }
-    | while_statement { $$ = $1; }
-    | "if" expression "then" statements elsif_then_statements else_statements "end"
+    | "while" expression "do" optional_statements elsif_do_statements else_statements "end"
+        {
+            boot::conditional_statements *body = new boot::conditional_statements($2, std::move($4));
+            $$ = new boot::while_statement(boot::make_position(@1), body, std::move($5), $6);
+        }
+    | "if" expression "then" optional_statements elsif_then_statements else_statements "end"
         {
             boot::conditional_statements *then = new boot::conditional_statements($2, std::move($4));
             $$ = new boot::if_statement(boot::make_position(@1), then, std::move($5), $6);
         }
-    | return_statement { $$ = $1; }
     | call_expression { $$ = $1; }
-    | "defer" statements "end" { $$ = new boot::defer_statement(boot::make_position(@1), std::move($2)); }
+    | "defer" optional_statements "end"
+        { $$ = new boot::defer_statement(boot::make_position(@1), std::move($2)); }
     | "case" expression "of" switch_cases else_statements "end"
         { $$ = new boot::case_statement(boot::make_position(@1), $2, std::move($4), $5); }
-switch_case: case_labels ":" statements { $$ = { .labels = std::move($1), .statements = std::move($3) }; }
+switch_case: case_labels ":" optional_statements
+        { $$ = { .labels = std::move($1), .statements = std::move($3) }; }
 switch_cases:
     switch_case "|" switch_cases
         {
@@ -447,13 +441,15 @@ case_labels:
             $$.emplace($$.cbegin(), $1);
         }
     | expression { $$.push_back($1); }
-statements:
-    statement ";" statements
+required_statements:
+    required_statements ";" statement
         {
-            std::swap($$, $3);
-            $$.insert($$.cbegin(), $1);
+            std::swap($$, $1);
+            $$.insert($$.cend(), $3);
         }
     | statement { $$.push_back($1); }
+optional_statements:
+    required_statements { std::swap($$, $1); }
     | /* no statements */ {}
 field_declaration:
     IDENTIFIER ":" type_expression { $$ = std::make_pair($1, $3); }
@@ -578,9 +574,11 @@ type_part:
     | "type" type_definitions { std::swap($$, $2); }
 formal_parameter:
     IDENTIFIER ":" type_expression { $$ = std::make_pair($1, $3); }
+formal_parameter_list:
+    "(" ")" {}
+    | "(" formal_parameters ")" { std::swap($$, $2); }
 formal_parameters:
-    /* no formal parameters */ {}
-    | formal_parameter "," formal_parameters
+    formal_parameter "," formal_parameters
         {
             std::swap($$, $3);
             $$.emplace($$.cbegin(), std::move($1));
diff --git a/boot/semantic.cc b/boot/semantic.cc
index bf086dd..b668f8e 100644
--- a/boot/semantic.cc
+++ b/boot/semantic.cc
@@ -252,10 +252,7 @@ namespace elna::boot
 
     void declaration_visitor::visit(return_statement *statement)
     {
-        if (statement->return_expression != nullptr)
-        {
-            statement->return_expression->accept(this);
-        }
+        statement->return_expression().accept(this);
     }
 
     void declaration_visitor::visit(defer_statement *statement)
diff --git a/gcc/elna-generic.cc b/gcc/elna-generic.cc
index 761344d..c96e28f 100644
--- a/gcc/elna-generic.cc
+++ b/gcc/elna-generic.cc
@@ -1297,13 +1297,12 @@ namespace elna::gcc
 
     void generic_visitor::visit(boot::while_statement *statement)
     {
-        std::string loop_identifier = statement->label.value_or("while");
         location_t prerequisite_location = get_location(&statement->body().prerequisite().position());
-        tree prerequisite_label_decl = build_label_decl(loop_identifier.c_str(), prerequisite_location);
+        tree prerequisite_label_decl = build_label_decl("while_do", prerequisite_location);
         auto prerequisite_label_expr = build1_loc(prerequisite_location, LABEL_EXPR,
                 void_type_node, prerequisite_label_decl);
         auto goto_check = build1(GOTO_EXPR, void_type_node, prerequisite_label_decl);
-        tree branch_end_declaration = build_label_decl(loop_identifier.c_str(), UNKNOWN_LOCATION);
+        tree branch_end_declaration = build_label_decl("while_end", UNKNOWN_LOCATION);
         tree branch_end_expression = build1_loc(UNKNOWN_LOCATION, LABEL_EXPR, void_type_node, branch_end_declaration);
 
         append_statement(prerequisite_label_expr);
@@ -1340,7 +1339,7 @@ namespace elna::gcc
 
     void generic_visitor::visit(boot::return_statement *statement)
     {
-        boot::expression *return_expression = statement->return_expression;
+        boot::expression *return_expression = &statement->return_expression();
         location_t statement_position = get_location(&statement->position());
         tree set_result{ NULL_TREE };
         tree return_type = TREE_TYPE(TREE_TYPE(current_function_decl));
diff --git a/include/elna/boot/ast.h b/include/elna/boot/ast.h
index 4de7bbd..6ba29f7 100644
--- a/include/elna/boot/ast.h
+++ b/include/elna/boot/ast.h
@@ -466,11 +466,13 @@ namespace elna::boot
     class return_statement : public statement
     {
     public:
-        expression *const return_expression{ nullptr };
+        expression *m_return_expression;
 
-        return_statement(const struct position position, expression *return_expression = nullptr);
+        return_statement(const struct position position, expression *return_expression);
         void accept(parser_visitor *visitor) override;
 
+        expression& return_expression();
+
         virtual ~return_statement() override;
     };
 
@@ -653,14 +655,10 @@ namespace elna::boot
 
     public:
         const std::vector<conditional_statements *> branches;
-        const std::optional<std::string> label;
         const std::vector<statement *> *alternative;
 
         while_statement(const struct position position, conditional_statements *body,
                 std::vector<conditional_statements *>&& branches, std::vector<statement *> *alternative = nullptr);
-        while_statement(const struct position position, conditional_statements *body,
-                std::vector<conditional_statements *>&& branches, const std::string& label,
-                std::vector<statement *> *alternative = nullptr);
         void accept(parser_visitor *visitor) override;
 
         conditional_statements& body();
diff --git a/source.elna b/source.elna
index 4fb3d65..822f6b7 100644
--- a/source.elna
+++ b/source.elna
@@ -154,7 +154,6 @@ proc exit(code: Int) -> !; extern
 *)
 
 proc reallocarray(ptr: ^Byte, n: Word, size: Word) -> ^Byte;
-begin
   return realloc(ptr, n * size)
 end
 
@@ -212,32 +211,26 @@ begin
 end
 
 proc is_digit(c: Char) -> Bool;
-begin
   return cast(c: Int) >= cast('0': Int) & cast(c: Int) <= cast('9': Int)
 end
 
 proc is_alpha(c: Char) -> Bool;
-begin
   return cast(c: Int) >= cast('A': Int) & cast(c: Int) <= cast('z': Int)
 end
 
 proc is_alnum(c: Char) -> Bool;
-begin
   return is_digit(c) or is_alpha(c)
 end
 
 proc is_space(c: Char) -> Bool;
-begin
   return c = ' ' or c = '\n' or c = '\t'
 end
 
 proc substring(string: String, start: Word, count: Word) -> String;
-begin
   return String(string.ptr + start, count)
 end
 
 proc open_substring(string: String, start: Word) -> String;
-begin
   return substring(string, start, string.length - start)
 end
 
@@ -339,12 +332,10 @@ begin
 end
 
 proc source_code_empty(source_code: ^SourceCode) -> Bool;
-begin
   return source_code^.empty(source_code^.input)
 end
 
 proc source_code_head(source_code: SourceCode) -> Char;
-begin
   return source_code.head(source_code.input)
 end
 
@@ -361,7 +352,6 @@ begin
 end
 
 proc source_code_expect(source_code: ^SourceCode, expected: Char) -> Bool;
-begin
   return ~source_code_empty(source_code) & source_code_head(source_code^) = expected
 end
 
@@ -375,7 +365,7 @@ var
 begin
   if escape = 'n' then
 	result^ := '\n';
-	successful := true;
+	successful := true
   elsif escape = 'a' then
 	result^ := '\a';
 	successful := true
@@ -419,12 +409,10 @@ proc skip_spaces(source_code: ^SourceCode);
 var
   current: Char
 begin
-  while ~source_code_empty(source_code) do
+  while ~source_code_empty(source_code) & is_space(source_code_head(source_code^)) do
     current := source_code_head(source_code^);
 
-    if ~is_space(current) then
-      return
-    elsif current = '\n' then
+    if current = '\n' then
       source_code_break(source_code)
 	end;
 	source_code_advance(source_code)
@@ -432,7 +420,6 @@ begin
 end
 
 proc is_ident(char: Char) -> Bool;
-begin
   return is_alnum(char) or char = '_'
 end
 
@@ -681,7 +668,7 @@ begin
 	end;
 	write_c(' ');
 
-	i := i + 1u;
+	i := i + 1u
   end;
   write_c('\n')
 end
@@ -962,7 +949,7 @@ begin
   result^.parse := false;
   result^.input := nil;
 
-  while i < argc do
+  while i < argc & result <> nil do
     parameter := argv + i;
 
     if strcmp(parameter^, "--lex\0".ptr) = 0 then
@@ -972,23 +959,24 @@ begin
     elsif parameter^^ <> '-' then
 	  if result^.input <> nil then
 		write_s("Fatal error: Only one source file can be given.\n");
-		return nil
-	  end;
-      result^.input := parameter^
+		result := nil
+	  else
+        result^.input := parameter^
+	  end
     else
       write_s("Fatal error: Unknown command line options: ");
 
       write_z(parameter^);
       write_s(".\n");
 
-      return nil
+      result := nil
     end;
 
     i := i + 1
   end;
-  if result^.input = nil then
+  if result <> nil & result^.input = nil then
     write_s("Fatal error: no input files.\n");
-	return nil
+	result := nil
   end;
 
   return result