use strict;
use warnings;

warn "Version $]";
warn "Prototype", prototype "CORE::sleep";



my $sleepcounter;

sleep 2;

BEGIN {
    my $old = \&CORE::sleep;

    *CORE::GLOBAL::sleep =  sub {
        warn  "start wrapper $_[0]";
        $sleepcounter += $_[0];
        $old->(@_);

    };
}


sleep 3;

warn "total sleep( $sleepcounter )";

##</code><code>##

Version 5.016003 at d:/Users/lanx/pm/core_sleep.pl line 4.
Prototype;$ at d:/Users/lanx/pm/core_sleep.pl line 5.
start wrapper 3 at d:/Users/lanx/pm/core_sleep.pl line 16.
total sleep( 3 ) at d:/Users/lanx/pm/core_sleep.pl line 26.