my @filenames
foreach my $file (@files)
{
  if( $file =~ m:/file-(\d+)-2.txt$: )
  {
    $filenames[$1] = $file;
  }
  else
  {
    warn "Unexpected file found: $file\n";
  }
}

foreach my $file (@files)
{
  print $file if defined $file;
}