Regarding this part of your suggested code:

foreach my $dirEntry (@dir){
  if(&SOME_TEST($dirEntry)){
    ...
    @dir = readdir(DIR);
  }
}
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As a rule, it is a Bad Idea™ to alter or replace the contents of an array within a "for" loop that is iterating over that array. Results of doing so may be "unpredictable" at best.

As it turns out, checking for existence of a file before doing "unlink" is actually unnecessary -- you are not checking the return status from "unlink", and frankly, why care whether you "unlink" a file that is non-existent? That sort of "error" is harmless and could safely be ignored.