#!/usr/bin/perl -wl
use strict;

my %data;
for (1..10000){
    my $str = "boy boy girl boy girl boy girl girl";
    my $l = int(rand(rindex($str,"boy") - 1));
    $str =~ s/^(.{$l}.*?)\bboy\b/$1man/;
    $data{$str}++;
}

print "$_: $data{$_}" for sort keys %data;