... despite my various solutions and workarounds from my nodes here and here being much better than the following, if you're hell-bent on only modifying sub printout, here's enough rope to shoot yourself in the foot: (Update: Note the following only works because of the absence of strict...)

sub printout {
  my ($lines, $_fh) = @_;
  my $fh = $_fh ? caller.'::'.$_fh : *STDOUT;
  foreach my $line (@{$lines}) {
    print $fh "$line\n";
  }
} # End printout;
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Though you may need to replace caller with the string "main" if printout gets called from another package. /shudder