This also works:

#!/usr/bin/perl
use strict;
use warnings;

my $data = "duck";
while(<DATA>) {
    chomp;
    my( $find, $replace ) = split ' ', $_, 2;
    if( $data =~ s[\Q$find][$replace]e ) {
        print "$data\n";
    }
}

__DATA__
duck luck
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