Add exists instruction

docs/syntax.md

@@ -116,6 +116,12 @@ Gets the type of a variable. Outputs a string which can be "int", "double", "boo
 
 Usage: `gettype $value &var`
 
+#### exists
+
+Checks if a variable exists with a direct reference. If the variable exists, outputs true. Otherwise outputs false.
+
+Usage `exists &var1 &var2`
+
 #### setlist
 
 Allows you to initialize a list.