I'd say the big ones are:
- Perl 5.8
- Decent Unicode
- Decent threading
- PerlIO layer
- Perl 5.10
- Smart match operator
- Defined-or operator
- given and when
- state
- say
- Perl 5.12
- Implicit strictures
- each(@array), keys(@array), values(@array)
- package Foo::Bar 1.23;
- Postfix form of when
- Yada-yada-yada operator
- Perl 5.14
- push $arrayref, @items, etc
- package Foo::Bar 1.23 { ... }
- s///r
- Perl 5.16
- __SUB__
- fc
I've specifically ignored any new pragmata and core modules, as those are often also available on CPAN for older versions.
perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'