For folks using Perl not built to support threads and wanting to try BrowserUk's example, here is the same thing using MCE::Hobo and MCE::Shared.

#! perl -slw
use strict;
use MCE::Hobo;
use MCE::Shared;

sub nap { select '','','', $_[0] }

tie my $done, 'MCE::Shared', 0;
my $hobo = mce_async( sub {
    $|++;
    until( $done ) {
        nap( 0.1 ),  printf "\r%s\t\t", '.' x $_ for 1 .. 10, reverse
+1 .. 10;
        nap( 0.01 ), printf "\r%s\t\t", '.' x $_ for 1 .. 10, reverse
+1 .. 10;
        nap( 0.8 );
    }
}, $done );

sleep 10;
$done = 1;
$hobo->join;
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