こんな計り方↓

#!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw/:all/;

my ($lf, $cr, $n) = ("\012", "\015", "\n");
my $str = "$n$cr$lf$lf${cr}1${cr}2${lf}3$cr${lf}4${n}5$n$cr$lf$lf$cr$n" x 100;

cmpthese -5, {
'1while' => sub {$_ = $str; 1 while s/[\012\015]$//;},
'1while_g' => sub {$_ = $str; 1 while s/[\012\015]$//g;},
quantifier => sub {$_ = $str; s/[\012\015]+$//;},
while_g => sub {$_ = $str; while (s/[\012\015]$//g){};},
while => sub {$_ = $str; while (s/[\012\015]$//){};},
};
__END__

同じwhileでもgオプションつけると微妙に速くなる
面白い