use 5.20.0;
use threads;

sub loop1 { do { print "loop1\n"; sleep 1 } while 1 }
sub loop2 { do { print "loop2\n"; sleep 1 } while 1 }

my $thr1 = threads->create('loop1');
my $thr2 = threads->create('loop2');

do { print "main\n"; sleep 1 } while 1;