#!/usr/bin/env perl

use strict;
use warnings;

### This eval code snippet works ###
eval(my $ref2 = "parent_ref");
####################################

my $string = "first_string ref[i] second_string $ref2.ref[i] third_string";
my $new_string;
my $i;

for ($i=0; $i<5; $i++) {
    print "$i : ";
    $new_string = $string; # don't clobber original string, else search-and-replace fails after first loop
    $new_string =~ s/\[i\]/\[$i\]/g;
    print "$new_string\n";
}