Curious... it seems that perl dumps core when undefing packages.

Foo.pm contains:

package Foo;
require Exporter;
@ISA = qw(Exporter);
@EXPORT = qw(hello say);
@EXPORT_OK = qw(hello say);

sub hello
{
"Hello, world!\n";
}

sub say
{
print @_;
}
[download]

If I do this (not including extraneous output):

$ perl -MFoo -de 42
> x %Foo::
(contents of Foo package)
> say hello
Hello, world!
> undef %Foo::
> x %Foo::
 empty array
> say hello
[download]

... abort with SIGSEGV in DB::DB. If I run this outside the debugger, it works fine. Running perl 5.6.1 on i686-pc-linux-gnu.