Or even simpler...

#!/usr/local/bin/perl

use warnings;
use strict;

for (qw(1 5 10 a 4 0 deadbeef 357 Albuquerque)) {
    warn "Bad input $_\n" and next unless /^([1-7])$/;
    print "Good input $1\n";
}
[download]

Update: erp! Left out untainting bit. Minor edit to untaint data.