C:\>perl -e "undef a"
Can't modify constant item in undef operator at -e line 1, at EOF
Execution of -e aborted due to compilation errors.

C:\>perl -v

This is perl, v5.6.1 built for MSWin32-x86-multi-thread
(with 1 registered patch, see perl -V for more detail)

Copyright 1987-2001, Larry Wall

Binary build 628 provided by ActiveState Tool Corp. http://www.ActiveState.com
Built 15:41:05 Jul  4 2001

##</code><code>##

$ perl -e 'undef a'
Can't modify constant item in undef operator at -e line 1, at EOF
Execution of -e aborted due to compilation errors.
$ perl -v

This is perl, version 5.005_02 built for PA-RISC1.1

Copyright 1987-1998, Larry Wall