use strict;
use warnings;

my $foo = 5;

print "Content-type: text/plain\n";
print "Content-disposition: inline; filename=foo.txt\n\n";

printf "Package: %s\n", __PACKAGE__;
printf "[%s] Before: %s\n", $$, $foo;

badness(\$foo, 5);
badness(\$foo, 5);
printf "[%s] After: %s\n", $$, $foo;

sub badness {
    my ($foo,$val) = @_;
    printf "[%s] badness: %s\n", $$, $$foo;
    $$foo += $val;
}