diff --git a/src/com/annimon/everlastingsummer/Lexer.java b/src/com/annimon/everlastingsummer/Lexer.java
index 35d370b..610a612 100644
--- a/src/com/annimon/everlastingsummer/Lexer.java
+++ b/src/com/annimon/everlastingsummer/Lexer.java
@@ -15,12 +15,12 @@ public final class Lexer {
         return new Lexer().process(input).getTokens();
     }
     
-    private static final String OPERATOR_CHARS = "=+-()[]$:";
+    private static final String OPERATOR_CHARS = "=+-()[]!$:";
     private static final TokenType[] OPERATOR_TYPES = new TokenType[] {
         TokenType.EQ,
         TokenType.PLUS, TokenType.MINUS, 
         TokenType.LPAREN, TokenType.RPAREN, TokenType.LBRACKET, TokenType.RBRACKET,
-        TokenType.COMMAND, TokenType.COLON,
+        TokenType.EXCL, TokenType.COMMAND, TokenType.COLON,
     };
 
     private static final Map<String, TokenType> KEYWORDS;
diff --git a/src/com/annimon/everlastingsummer/Parser.java b/src/com/annimon/everlastingsummer/Parser.java
index 5a3683d..5eb4d4d 100644
--- a/src/com/annimon/everlastingsummer/Parser.java
+++ b/src/com/annimon/everlastingsummer/Parser.java
@@ -377,7 +377,7 @@ public final class Parser {
     }
     
     private boolean ifStatement() {
-        final Expression condition = primary();
+        final Expression condition = expression();
         consume(TokenType.COLON);
         
         if (condition.eval() == 0) {
@@ -421,6 +421,9 @@ public final class Parser {
         if (match(TokenType.PLUS)) {
             return primary();
         }
+        if (match(TokenType.EXCL)) {
+            return new ValueExpression( primary().eval() != 0 ? 0 : 1 );
+        }
         return primary();
     }
     
diff --git a/src/com/annimon/everlastingsummer/TokenType.java b/src/com/annimon/everlastingsummer/TokenType.java
index 1349419..3e17aeb 100644
--- a/src/com/annimon/everlastingsummer/TokenType.java
+++ b/src/com/annimon/everlastingsummer/TokenType.java
@@ -18,6 +18,7 @@ public enum TokenType {
     RPAREN,
     LBRACKET,
     RBRACKET,
+    EXCL,
     COLON,
     
     // ключевые слова