diff --git a/examples/hello_world.csq b/examples/hello_world.csq
new file mode 100644
index 0000000..21f1463
--- /dev/null
+++ b/examples/hello_world.csq
@@ -0,0 +1,5 @@
+include stdio;
+
+void! main() {
+    printf("Hello, World!\n");
+}
diff --git a/include/csquare/lexer/lexer.h b/include/csquare/lexer/lexer.h
index 980391c..16a9c6a 100644
--- a/include/csquare/lexer/lexer.h
+++ b/include/csquare/lexer/lexer.h
@@ -49,6 +49,7 @@
   T(T_SEMICOLON, "SEMICOLON")                                                  \
   T(T_AND, "AND")                                                              \
   T(T_OR, "OR")                                                                \
+  T(T_EXCLAMATION, "EXCLAMATION MARK")                                         \
                                                                                \
   T(T_KW_DO, "DO")                                                             \
   T(T_KW_IF, "IF")                                                             \
@@ -112,7 +113,7 @@ void add_token(token_list *list, token *tk);
 
 #define isws(c) (c == ' ' || c == '\t' || c == '\n' || c == '\r')
 #define isdigit(c) (c >= '0' && c <= '9')
-#define isalpha(c) (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z')
+#define isalpha(c) ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'))
 
 #define LEX_FUNC_ARGS const char *p, int *len
 token *lex_symbol(LEX_FUNC_ARGS);
diff --git a/makefile b/makefile
index 9735213..36124cd 100644
--- a/makefile
+++ b/makefile
@@ -1,10 +1,12 @@
 include config.mk
 
-.PHONY: all clean directories
+.PHONY: all clean directories rebuild
 
 # Default target
 all: directories $(TARGET)
 
+rebuild: clean all
+
 directories:
 	@mkdir -p $(BUILDDIR) $(BINDIR) $(shell find $(SRCDIR) -type d | sed 's/$(SRCDIR)/$(BUILDDIR)/')
 
diff --git a/src/csquare/opt-common.c b/src/csquare/opt-common.c
index 59b8996..c20a94e 100644
--- a/src/csquare/opt-common.c
+++ b/src/csquare/opt-common.c
@@ -9,6 +9,7 @@ static const opt_map_t opts[] = {{"--info", "-i", OPT_KIND_FUNC,
                                   handle_info}};
 
 static void handle_info(csq_options *opts, const char *_) {
+  (void)_;
   (void)opts;
   printf("Csquared - %s (%s)\n", CSQ_VERSION, __DATE__);
   printf("Authors: %s\n", CSQ_AUTHORS);
diff --git a/src/lexer/lex_symbol.c b/src/lexer/lex_symbol.c
index 310ff0c..23a04f0 100644
--- a/src/lexer/lex_symbol.c
+++ b/src/lexer/lex_symbol.c
@@ -7,9 +7,11 @@ const struct {
     {"==", T_EQ},          {"!=", T_NEQ},          {">=", T_GREATER_EQUALS},
     {"<=", T_LESS_EQUALS}, {"+=", T_ADD_ASSIGN},   {"-=", T_SUB_ASSIGN},
     {"/=", T_DIV_ASSIGN},  {"*=", T_MUL_ASSIGN},   {"&&", T_AND},
-    {"||", T_OR},          {"=", T_ASSIGN},        {"+", T_ADD},
-    {"-", T_SUB},          {"/", T_DIV},           {"*", T_MUL},
-    {">", T_GREATER},      {"<", T_LESS},          {"(", T_OPEN_PAREN},
+    {"||", T_OR},
+
+    {"=", T_ASSIGN},       {"+", T_ADD},           {"-", T_SUB},
+    {"/", T_DIV},          {"*", T_MUL},           {">", T_GREATER},
+    {"<", T_LESS},         {"!", T_EXCLAMATION},   {"(", T_OPEN_PAREN},
     {")", T_CLOSE_PAREN},  {"{", T_OPEN_BRACE},    {"}", T_CLOSE_BRACE},
     {"[", T_OPEN_BRACKET}, {"]", T_CLOSE_BRACKET}, {".", T_PERIOD},
     {",", T_COMMA},        {":", T_COLON},         {";", T_SEMICOLON}};
diff --git a/src/lexer/lexer.c b/src/lexer/lexer.c
index c1f7c94..8ba596c 100644
--- a/src/lexer/lexer.c
+++ b/src/lexer/lexer.c
@@ -125,6 +125,7 @@ token_list *lex(const char *src) {
     add_token(list, tk);
   }
 
+  add_token(list, new_token(p, 0, T_EOF));
   return list;
 }