#!/usr/bin/env perl

use strict;
use warnings;
use Data::Dump;

my $sum = 0;

SUM: while (<STDIN>) {
    chomp;
    last SUM if /q/i;
    if ( !/[\d\s]+/ ) {
        print qq(Enter only numbers!\n);
        # $sum = 0;
        last SUM;
    }
    my @array = split;
    dd \@array;
    for (@array) {
        if ( ( $_ > 0 ) && ( $_ < 21 ) ) {
            $sum += $_;
        }
        else {
            print qq(Too much!\n);
            last SUM;
        }
    }
    print qq(\$sum = $sum\n);
    undef @array;
}

print qq(This is the end!\n);

__END__
[download]