use strict;
use warnings;
use Benchmark 'cmpthese';

my $str = 'FOO' x 14 . 'ZOOCOO' . ('FOO' x 7);

for my $subName (qw(doSubZ doSubB doSubX doRegZ doRegB)) {
    my $result = main->can($subName)->();

    $result //= '--undef--';
    print "$subName: $result\n";
}

cmpthese(
    -1,
    {
        'substrindexZ' => \&doSubZ,
        'substrindexB' => \&doSubB,
        'regexpZ'      => \&doRegZ,
        'regexpB'      => \&doRegB,
    }
);


sub doSubZ {
    return undef if -1 == (my $idx = index ($str, 'ZOO'));
    return substr ($str, $idx, 6);
}


sub doSubX {
    return substr ($str, index ($str, 'BOO'), 6);
}


sub doSubB {
    return undef if -1 == (my $idx = index ($str, 'BOO'));
    return substr ($str, $idx, 6);
}


sub doRegZ {
    $str =~ /(ZOO.{3})/;
    return $1;
}


sub doRegB {
    $str =~ /(BOO.{3})/;
    return $1;
}

##</code><code>##

doSubZ: ZOOCOO
doSubB: --undef--
doSubX: O
doRegZ: ZOOCOO
doRegB: --undef--
                  Rate      regexpZ substrindexZ substrindexB      regexpB
regexpZ      1215237/s           --         -45%         -70%         -79%
substrindexZ 2198729/s          81%           --         -45%         -62%
substrindexB 4003188/s         229%          82%           --         -30%
regexpB      5733702/s         372%         161%          43%           --