I was having trouble building expressions for Expression and Validator widgets in Composer. I had a widget on the page named "name". I wanted to validate that the value was non-null, so I created a Validator widget and configured a parameter called NameValue. When I entered the expression [ NameValue!=="" ], Composer told me "You cannot use the eval function". After playing with it for quite some time, I discovered that composer appears to be doing a simple indexOf test for eval (as well as alert - there might be more). So the expression cannot contain any case form of eval or alert (Nam eVal ue). This also generates the error no matter where the string appears - [ GoodName==="NameValue" ] is also invalid to Composer.