use warnings;
use strict;

use Benchmark qw(:all);

open my $fh, '<', $ARGV[0] or die $!;

cmpthese(1000, {
                while_no_parens => '_while_no_parens',
                while => '_while',
         });
sub _while_no_parens {
    seek $fh, 0, 0;
    my $count=0;
    while(<$fh>){
      while($_=~/M+/g){
          $count++;
      }
    }
#    print "while w/o: $count\n";
}
sub _while {
    seek $fh, 0, 0;
    my $count=0;
    while(<$fh>){
      while($_=~/(M+)/g){
          $count++;
      }
    }
#    print "while: $count\n";
}

__END__
                  Rate           while while_no_parens
while           15.0/s              --            -11%
while_no_parens 16.9/s             13%              --