#!/usr/bin/perl -w
use strict;

my %horoscopes = (
    'homer' => 'pisces',
    'marge' => 'sagitarius',
    'bart'  => 'cancer',
    'libra' => 'libra'
);

capitalize(\%horoscopes);

sub capitalize {
    my $hash = shift;
    for my $key (keys %{$hash}) {
        $hash->{uc $key} = $hash->{$key};
        delete $hash->{$key};
    }
}