Current Perl documentation can be found at perldoc.perl.org.
Here is our local, out-dated (pre-5.6) version:
In general, you don't ``declare'' a structure. Just use a (probably anonymous) hash reference. See the perlref manpage and the perldsc manpage for details. Here's an example:
$person = {}; # new anonymous hash $person->{AGE} = 24; # set field AGE to 24 $person->{NAME} = "Nat"; # set field NAME to "Nat"
If you're looking for something a bit more rigorous, try the perltoot manpage.