There are a lot of things that Perl 6 adopted from other languages. Besides a lot of Perl 5 influence, Haskell in particular can be pointed to as strongly influential.
There are, however, a few language features which I've not seen in other languages. One I've mentioned is the Whatever Star. Another is "adverbs".
First let's talk about Pair. A Pair is exactly what it sounds -- a data structure that contains two things. In this case a Pair has a key and a value:
my $p = Pair.new(key => "age", value => 5); say $p # output: age => 2
Pairs are very common, so they have some literal syntax to build them. The most common is "=>", sometimes called the "fat arrow", which is a binary operator that builds a Pair -- key on the left, value on the right:
my $p = age => 5; say $p # output: age => 2
Notice that "age" wasn't put in quotes. The pair constructor auto-quotes the thing on the left, again to optimize for this common case. You can wrap the left in ()'s to force it to be a value.
Colon-Pair notation is another literal syntax for declaring a Pair, and here is where things start to get different:
my $x = 'cat'; :foo # 'foo' => True :foo(5) # 'foo' => 5 :foo('dog') # 'foo' => 'dog' :foo($x) # 'foo' => 'cat' :foo<bar> # 'foo' => 'bar' :foo<bar baz> # 'foo' => ('bar', 'baz') :foo<$x> # 'foo' => '$x' :foo<<$x>> # 'foo' => 'cat' :foo<<$x dog>> # 'foo => ('cat', 'dog')
The basic idea is you have a key that comes after the colon, and a value that comes in parenthesis or brackets after that. Unlike "=>" notation, this has a DEFAULT value of True. It also allows you to auto-quote the value side by using bracket notation (like you can do with Hashes).