Since that known values are in a hash, no need to loop through. Just check if the element exists.

#!/usr/bin/perl -w
use strict;
my %known = ("foo" => "FOO", "bar" => "BAR", "baz" => "BAZ");
print "Talk to me, Goose.";
my $input = <STDIN>; chomp($input);

(exists $known{lc $input} &&
    print "You gave us $input, which equates to $known{lc $input}.\n")
    || print "Not a match" ;
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