I am writing a quick subroutine to grab a list of files in a directory and return it as an array...

Just a side note: since the caller knows which directory is supposed to be scanned (and should also know that it's looking only for files whose names match "*.mp3" or something to that effect), there's no need for a subroutine call.

The code that would call your subroutine could just do this instead:

my @mp3files = <$path/*.mp3>;
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(assuming that $path is what would have been passed when calling your subroutine). That use of angle brackets in perl is referred to as a "file glob".