I get the same thing.

From perldoc Date::Manip

       Date::Manip must be able to determine the timezone the user is in.  It
       does this by looking in the following places:

          $Date::Manip::TZ (set with Date_Init or in Manip.pm)
          $ENV{TZ}
          the unix `date` command (if available)
          $main::TZ
          /etc/TIMEZONE
          /etc/timezone

       At least one of these should contain a timezone in one of the supported
       forms.  If none do by default, the TZ variable must be set with
       Date_Init.

My guess is that, like on my system, TZ isn't set. what isn't clear is why the unix date command isn't getting used - like yours, mine shows the local timezone.

The only thing I've found on my system is /etc/adjtime:

0.001227 1061666277 0.000000
1061666277
UTC

--Bob Niederman, http://bob-n.com

All code given here is UNTESTED unless otherwise stated.