Does the following code do what you need? It's basically what BrowserUk recommended, but lc is better than uc. (... because I said so!... and, besides, I wrote it before I saw BrowserUk's message! :)) ...

use strict;
use warnings;
my %known = (
    "foo" => "FOO",
    "bar" => "BAR",
    "baz" => "BAZ",
);

while ( <STDIN> ) {
    chomp;
    my $input = $_;

    for ( keys %known ) {
        if ( lc($input) eq $_ ) {
            print "You gave us $input, which equates to " . $known{lc(
+$input)};
            print ". Have a nice day\n";
        }
    }
}
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--
-- Ghodmode