Controlling Laziness
Laziness has its problems (and when you try to learn Haskell you'll notice how weird their IO system is because Haskell is both lazy and free of side effects), and sometimes you don't want stuff to be lazy. In this case you can just prefix it with eager.

my @list = eager map { $block_with_side_effects }, @list;
On the other hand only lists are lazy by default. But you can also make lazy scalars:

my $ls = lazy { $expansive_computation };

Perl 6 embraces the idea of multi threading, and in particular automated parallelization. To make sure that not all threads suffer from the termination of a single thread, a kind of "soft" exception was invented.

When a function calls fail($obj), it returns a special value of undef, which contains the payload $obj (usually an error message) and the back trace (file name and line number). Processing that special undefined value without check if it's undefined causes a normal exception to be thrown.

my @files = </etc/passwd /etc/shadow nonexisting>; my @handles = hyper map { open($_) }, @files;
In this example the hyper operator tells map to parallelize its actions as far as possible. When the opening of the nonexisting file fails, an ordinary die "No such file or directory" would also abort the execution of all other open operations. But since a failed open calls fail("No such file or directory" instead, it gives the caller the possibility to check the contents of @handles, and it still has access to the full error message.

If you don't like soft exceptions, you say use fatal; at the start of the program and cause all exceptions from fail() to be thrown immediately.