In addition to Data::Dumper and friends, the perl debugger is an excellent tool to slowly dive into a data structure, and understand how to access it.

Here is a debugger session, based on a made-up structure, similar to yours:
I have interjected comments starting with >>

$ perl -dE 'my @revs=([{author=>"myid",date=>"2013-06-21"},2,3]); say 
+$revs[0]{date}'

Loading DB routines from perl5db.pl version 1.33
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(-e:1):    my @revs=([{author=>"myid",date=>"2013-06-21"},2,3]);
+ say $revs[0]{date}
>>>> Step into the initialization of the structure ....
  DB<1> s
main::(-e:1):    my @revs=([{author=>"myid",date=>"2013-06-21"},2,3]);
+ say $revs[0]{date}

>>>>>*** Looking at the whole structure (Not a good idea if it is larg
+e)
  DB<1> x @revs
0  ARRAY(0x1765270)
   0  HASH(0x1765210)
      'author' => 'myid'
      'date' => '2013-06-21'
   1  2
   2  3

>>>>> Slow dive - We know @revs is an ARRAY - let us see what TYPE the
+ first (0) element is :
  DB<2> x ref $revs[0]
0  'ARRAY'

>>>> OK - so it is an 'ARRAY' - lets examine the TYPE of the first (0)
+ index.
  DB<7> x ref $revs[0][0]
0  'HASH'

>>> Aha - so $revs[0][0] is a HASHREF - lets see what KEYS are availab
+le...
  DB<9> x keys %{ $revs[0][0] }
0  'date'
1  'author'

>>>> Now we could do another "ref', but assuming this will result in a
+ target value, we simply try a key:
  DB<10> x $revs[0][0]{date}
0  '2013-06-21'

>>> end the debug session with 'quit'
  DB<11> q
[download]

so Now we know why "$revs[0]{date}" did not work.