Yet another solution (without claiming efficiency over previous solutions) 

#!/usr/bin/perl -wl
use strict;
my $str = "boy boy girl boy girl boy girl girl";
my $l = int(rand(rindex($str,"boy") - 1));
$str =~ s/^(.{$l}.*?)\bboy\b/$1man/;
print $str;

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--
Regards
- Samar

In reply to Re: Randomly regex substitute by samarzone
in thread Randomly regex substitute by Anonymous Monk

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