my @array1 = unique($filename1);

sub unique {
  my ($file) = shift;
  my (%seen);
  open my $fh, '<', $file or die "Could not open $file\n";
  while(<$fh>) {
    chomp;
    $_ =~ m/(RC=\d{4})/;
    $seen{$_} = 1;
  }
  close $fh;
  return keys %seen;
}