my %mapping = 
  (
  '[a-zA-A0-9]+' => 'A',
  );

my $summary = '';

CHUNK: while (length $filedata)
{
  foreach my $reg (keys %mapping)
  {
    if ($filedata =~ s/^$reg//)
    {
      $summary .= $mapping{$reg};
      next CHUNK;
    }
  }
  die "Chunk starting with '". substr($filedata, 0,10) . "' did not match any rules!";
}