#!/usr/bin/perl -l

use strict;

my $find="find=1";
my $repl="repl:2";

for my $trial (qw/find=1 Find=1 FIND=1 fInD=1/) {
    $_ = "here is >$trial< data";
    s/\b($find)\b/ uc($repl) | ( $1 ^ uc($1) ) /eig;
    print
}

##</code><code>##

here is >repl:2< data
here is >Repl:2< data
here is >REPL:2< data
here is >rEpL:2< data