use threads;

sub YourSub {
    ...
    return $result;
}

...

my $thread = threads->new( \&YourSub, $arg1, $arg2, ... );

# If your not interested in  the result from the sub then
# $thread->detach;
....
# Otherwise, this will retrieve the return value.
# Note: This will block until the thread finishes.
# One (of several) things missing from the API as it stands
# is any way to determine if the thread has finished 
# without blocking.
my $result = $thread->join;