RFC-24, implementation of item 3.2: parent references in PERL

[Umberto Nicoletti]

As I have already done for Python and C# here comes a patch for PERL
that implements item 3.2 of RFC24.
The patches are all attached to:

http://trac.osgeo.org/mapserver/ticket/2442

Unless I get negative feedback I'll apply the patches for Perl and
Python in the next weeks.

Best regards,
Umberto