use strict; use warnings;
use feature 'say';
use Scalar::Util 'looks_like_number';

say "Please input numbers to be summed. Crtl-D to stop";

my $user_input;

while ( <STDIN> ) {
    $user_input .= $_;
}

total( $user_input );

sub total {
    my $in = shift or die 'No numbers provided!';

    my $user_total = 0;

    for my $line ( split "/n", $in ) {
        chomp $line;
        for my $num ( split /\W+/, $line ) {
            die "$num doesn't look like a number!" if not looks_like_number( $num );
            $user_total += $num;
        }
    }

    say "Total: $user_total";
}

__END__