5.20 was the new shiny for 2014 in May, but 5.20.1 was launched in August
with some minor corrections. It also came with a memory leak invoked by
multiple iterations of an extremely complicated regex, but that already
has a patch if anyone hits it again.

There are some experimental features for subroutine signatures and prototypes
that those who care about such things can play with, but the rest of us will
probably leave alone for a release or two.

rand is now consistent across all platforms, but it's still not crypto-safe

There's an experimental form of postfix dereferencing, (object envy)?

Probably the major addition: Hashes and arrays can now be sliced

Starting in Perl 5.20, a hash slice operation with the % symbol is a variant
 of slice operation returning a list of key/value pairs rather than just values:

    %h = (blonk => 2, foo => 3, squink => 5, bar => 8);
    %subset = %h{'foo', 'bar'}; # key/value hash slice
    # %subset is now (foo => 3, bar => 8)

However, the result of such a slice cannot be localized, deleted or used in 
assignment. These are otherwise very much consistent with hash slices using 
the @ symbol.

Index/Value Array Slices

Similar to key/value hash slices (and also introduced in Perl 5.20), the % array slice syntax returns a list of index/value pairs:

    @a = "a".."z";
    @list = %a[3,4,6];
    # @list is now (3, "d", 4, "e", 6, "g")

Unicode is up to 6.3, although Perl can be compiled to earlier versions

There's more support for locales, especially with Utf-8

The special variables $a and $b are exempt from "used once" warnings, which
provides an additional reason for yelling at people who use them as variable
names in examples. (Given the temptation, I wish an obscure pair like $n and $o
had been picked for the job.)

Data::Dumper's output may have changed, in which case tests dependent on it
will fail. The delta suggests a fix.

More modules have been marked for removal from core, most notably CGI

Perl's now available for some new platforms:

Android

Perl can now be built for Android, either natively or through cross-compilation,
for all three currently available architectures (ARM, MIPS, and x86), 

Bitrig

Compile support has been added for Bitrig, a fork of OpenBSD.

FreeMiNT

Support has been added for FreeMiNT, a free open-source OS for the Atari ST 

Synology
Synology ships its NAS boxes with a lean Linux distribution (DSM) on relative 
cheap CPU's 

and discontinued on a few, most notably EBCDIC platforms, which would surely
affect IBM mainframes?

Lots of bug fixes, many bugs introduced by 5.18 changes (and a few 5.16).

2nd obituary of 20-something Perl enthusiast - hope this isn't a trend.