package MyClass;
my $cnt;

sub new {
    return bless { cnt => 0 };
}

sub gimme_sweet_love {
    my $self = @_;
    $self->{cnt} += 1;
    return "hell yeah"
}

sub cnt {
    my $self = @_;
    return $self->{cnt}
}

package main;
use strict;
use warnings;

local $\ = $/;
my $match = "hell yeah";
my $obj = MyClass->new();
my $re = qr/(??{ ${obj}->gimme_sweet_love })/;

print "\$match value:", $match;
print "HURAY (m)"  if  $match =~ m/$re/;
print "count = ".$obj->cnt;

$match = "hell no";
print "\$match value:", $match;
print "HURAY (m)"  if  $match =~ m/$re/;
print "count = ".$obj->cnt;
[download]

$match value:hell yeah
HURAY (m)
count = 1
$match value:hell no
count = 9
[download]

So, when there's no match, the above method $obj->gimme_sweet_love is executed "the number of chars" times, could someone tell me why?

when there's a match, the method is executed only once.