...
use MCE::Loop;
use MCE::Shared;
use MCE::Mutex;

my $result = MCE::Shared->hash;
my $mutex = MCE::Mutex->new
...

mce_loop {
    my @data = $fetch->($_);
    sleep AMOUNT;
    $mutex->enter( $result->set( $_ => \@data ) );
}
@urls;

...