Quick and dirty run lengths

gistfile1.pl

sub run_lengths {
  return unless @_ > 0;
  my $prev = shift @_;
  my @runs = [$prev, 1];
  for (@_) {
    if ($_ eq $prev) {
      $runs[-1]->[1]++;
      next;
    }
    push @runs, [$_, 1];
    $prev = $_;
  }
  @runs;
}