Merlyn & Dmitri: Thank you for your assistance. I had some print statements in the subroutine, so I know that the actual matching of array against hash does work and $ary_element is a defined value before I try to push it. Here is what I'm doing with @_ (this still doesn't work):

sub blah
{
  @array = match_files(\@array, \%hash);
  print "@array \n";
}

sub match_files
{
  @files = ();
  my($array, $hash) = @_;
  my(@array) = @$array;
  my(%hash) = %$hash;

  foreach $ary_element (@array)
  {
     foreach $hash_key( keys ( %hash ))
     {
         # do my comparison here
     }
     
     # if i get a match
     print "$ary_element\n"; # prints defined value
     push (@files, $ary_element);
     return @files;
   }
}
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