I have this expression:

......onclick="if(! confirm('#{labels['general.confirmDelete']}')) return false;">.....

And validation give me next errors:

Syntax error on token ")", ; expected   
Syntax error on token "confirmDelete", ( expected after this token   
Syntax error, insert ") BlockStatement" to complete ProgramElements   
Syntax error, insert ") BlockStatement" to complete ProgramElements   
Syntax error, insert ")" to complete MethodInvocation   

For me expression is correct