This works for me:

#! /usr/bin/perl

use strict ;
use warnings ;

my @arr = qw/ cidaris see doing / ;

my $str = <<'EOD' ;
Hello, ##REPLACE##.
Nice to ##REPLACE## you.
How are you ##REPLACE## today?
EOD

my $i = 0 ;
$str =~ s/##REPLACE##/$arr[$i++]/g ;

print $str ;
[download]