The Damian CONWWAY's module can help you :
http://search.cpan.org/~dconway/IO-Prompt-v0.99.4/lib/IO/Prompt.pm

#!/usr/bin/perl 

use strict;
use warnings;
use IO::Prompt;

my $example = "Example";

( prompt "Enter your choice [y/n] : ", -yes_no )
?
print uc($example), "\n"
:
print lc($example), "\n";
[download]

OUTPUT :
Enter your choice [y/n] : y
EXAMPLE
Enter your choice [y/n] : n
example
Enter your choice [y/n] : (Please answer 'y' or 'n')
[download]

HTH,
PooLpi