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

my $line="One two three four five";
my @chunks;
if(@chunks = $line =~ m/(one)\s(two)\s(three)\s(four)\s(five)/i){
    $chunks[0] =~ s/One/ONE/;   # Change the first chunk
    $chunks[1] =~ s/two/tWo/;   # Change the second chunk
    # ...
}
print "@chunks\n";

##</code><code>##

ONE tWo three four five