KM Thinks Matching Variables Don't Match

I have an "if then else" action whose sole condition is that the title of the front window (%WindowName%1%) not match the variable "currentWindow". The macro (which ultimately resizes the front window) seems to work for all but one application (MailMate). For some reason, when MailMate is the front window, Keyboard Maestro thinks the title does not match the variable even when it does. Here's a screenshot.

I'm wondering if this is related to the parentheses in the window title, but I can't figure out why this is happening or how to fix it.

In Keyboard Maestro terminology, “match” means regular expression.

Since the variable contains regular expression characters that have a meaning other than themselves (the brackets), the match fails for this window.

Use “title is not” instead of “title does not match”.