Perl also has unless() for the very purpose in OP, which is a more sensible choice.

Oh, and if you need to reinforce your belief that Perl is a mess, the single-quote character can be used as a package separator instead of “::”. This was set in the 90s when nobody was quite sure of the right syntax for package separators, so it borrowed “::” from C++ and the single quote from Ada (I think).

That means the ifn't() in OP can be interpreted as calling the t() function on the ifn package.

The “::” separator is vastly preferred, though. Single quotes run havoc on syntax highlighting text editors (since they can also be used for strings). About the only time I’ve seen it used is a joke module, Acme::don't.