#!/usr/bin/perl
use strict;
use warnings;
my $stdout_mixed_with_stderr = `perl print_and_warn.pl 3>&1 2>&3 3>&- 1>&-`;
print "BEGIN\n\n$stdout_mixed_with_stderr\nEND\n";
# output below
__END__
BEGIN

warning 1
warning 2
warning 3
warning 4
warning 5
warning 6
warning 7
warning 8
warning 9
warning 10

END