pretendeavor, your update isn't doing what toolic meant!

if ($answer !~ /\D+/) { ## if answer doesn't have any non-digits
        print "Please enter a number only\n"; ## Really?
        next;
    }
[download]

when you want

if ($answer =~ /\D/) { 
## if answer has any non-digits 
        print "Please enter a number only\n";
        next;
    }
[download]

the character escape \D includes '-' the minus sign hence the positive integer comment.
With character classes, capitalisation usually means the opposite (i.e. \d = all digits, \D all non-digits.
The '+' sign means 'one or more matches' not positive! See perlre.

Other than that I like it! Got to get the kids started early!!