use strict;
use warnings;
use Benchmark qw/ cmpthese /;

my $R = 'R' x 42_000;
my $Q = 'Q' x 42_000;

sub foo {
    my $c = shift;

    pos $$c = 0;
    while ( 1 ) {
        next if $$c =~ /\G\d+R/;
        last unless $$c =~ /\w/g;
    }
}

cmpthese -3, { 
    R => sub { foo( \$R )},
    Q => sub { foo( \$Q )},
}

[download]

C:\>perl test.pl
    Rate     Q     R
Q 1.30/s    --  -96%
R 30.9/s 2279%    --

[download]

I'd expect both strings should behave the same (match fails immediately) in line which starts with next, but it's obviously not so. There's some weird internal "optimization" going on here, but why?

And it's not just idle curiosity, dear monks. Look here. Syntax like 42 0 R is "indirect object" ("R" for "reference"), i.e. "R" is kind of "special". It so happens that huge (150 Mb) page content has no "R"'s, and it takes forever to parse this string :(.

In reply to Why is Perl suddenly slow in THIS case? by vr

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