IMO in general grep and map shouldn't be chained together, map can do greps job without having retraverse the array.

return (map{-e "$_/$target" ? "$_/$target" : ()} @dir)[0];
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And frankly why bother with map and grep at all? This is much more efficient.

sub FileFinder {
  my $target=shift;
  -e "$_/$target" && return "$_/$target" foreach @_;
  undef 
}
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Oh and before the premature optimization police arrest me, remember that we are searching a filesystem (possible remote etc) here. That call to -e could take a while and if we have to do more of them than we really need to then we could end up wasting a lot of time.

Adjust the file test to your taste ;-)

Yves / DeMerphq
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Writing a good benchmark isnt as easy as it might look.