my @choices = (
    'system1',
    'system2',
    'system3',
    # ...
);

#displays the menu
sub menu {
    print "Please pick which system you wish to FTP to:\n";
    for (my $i = 0; $i < @choices; $i++) {
        printf "%3d)  %s\n", $i+1, $choices[$i];
    }
    chomp(my $option = <>);
}