>perl -v

This is perl, v5.8.2 built for MSWin32-x86-multi-thread
...
Binary build 808 provided by ActiveState Corp.
Built Dec  9 2003 10:19:40
...

>perl -wMstrict -le
"my $ue = pack 'u*', '';
 print 'ue undefined' unless defined $ue;
 print qq{:$ue:};
 my $ud = unpack 'u*', $ue;
 print 'ud undefined' unless defined $ud;
 print qq{:$ud:};
"
::
ud undefined
Use of uninitialized value in concatenation (.) or string at ...
::