I rebuilt rxvt-unicode with the patch and the urxvt segfaults at exit no longer occurs. For me this is fixed.
--- a/src/rxvtperl.xs.orig
+++ b/src/rxvtperl.xs
@@ -376,6 +376,7 @@ rxvt_perl_interp::~rxvt_perl_interp ()
{
if (perl)
{
+ localise_env set_environ (perl_environ);
perl_destruct (perl);
perl_free (perl);
PERL_SYS_TERM ();
Cheers
Holger...

