it's easy to do it with POE

#!/usr/bin/perl
# vim: set et sta ts=4 sw=4 sts=4:
# vi: set ts=4:
# #
use strict;
use warnings;

use POE;

POE::Session->create(
  inline_states => {
    _start    => \&handler_start,
    fun1      => \&fun1,
    fun2      => \&fun2,
    _stop     => \&handler_stop,
});

POE::Kernel->run();
exit;

sub handler_start {
    my ($kernel, $heap, $session) = @_[KERNEL, HEAP, SESSION];
    print "Starting !\n";
    $kernel->yield( 'fun1' );
    $kernel->yield( 'fun2' );
}

sub fun1 {
    my ($kernel, $heap, $session) = @_[KERNEL, HEAP, SESSION];
    print "I'm function 1!\n"; 
    $kernel->delay(fun1 => 6);
}

sub fun2 {
    my ($kernel, $heap, $session) = @_[KERNEL, HEAP, SESSION];
    print "I'm FUNCTION 2!\n"; 
    $kernel->delay(fun2 => 6);
}

sub handler_stop {
    print "Stop !!\n";
}
[download]

Output:

Starting !
I'm function 1!
I'm FUNCTION 2!
I'm function 1!
I'm FUNCTION 2!
I'm function 1!
I'm FUNCTION 2!
...
[download]