If you use strict.pm you will get slightly more information under 5.6. In 5.005 you will not, though you get a more bizarre error if you replace the print with print "$$var";

The key point that causes the problem is likely that the assignment is in the process of wiping out $var as you are trying to also dereference it. Depending on the exact order of actions, you can easily get into nasty little boundary conditions.

Perl should still not segfault though...