You need to be a little more careful about how you handle the return value of do:

If do cannot read the file, it returns undef and sets $! to the error.

If do can read the file but cannot compile it, it returns undef and sets an error message in $@ .

Always check $@ first, as compilation could fail in a way that also sets $! .

If the file is successfully compiled, do returns the value of the last expression evaluated.

(Emphasis mine.)

You're testing for a false return value... but you could get a false value even if do succeeding in reading and executing the file.