print "$in was not a number!"; input() unless $in =~ /\d/;

##</code><code>##

sub input {
    my $arrayref=shift;
    print "\nSo far you've guessed @$arrayref."
          if $arrayref;
    print "\nWhat is your guess?\n";
    chomp <STDIN>;
    my $in=<STDIN>;
    print "$in wasn't a number!";input() unless $in =~ /\d/;
}