This is in-house developed patch reported at

Expectation is that future perl versions will contain the fix.

--- perl-5.12.5/util.c 2014-05-28 12:10:02.250325812 +0200

+++ perl-5.12.5/util.c 2014-05-28 12:09:34.437338588 +0200

@@ -1712,7 +1712,7 @@ Perl_my_setenv(pTHX_ const char *nam, co

my_setenv_format(environ[i], nam, nlen, val, vlen);

} else {

# endif

-# if defined(__CYGWIN__) || defined(EPOC) || defined(__SYMBIAN32__) || defined(__riscos__)

+# if defined(__CYGWIN__) || defined(EPOC) || defined(__SYMBIAN32__) || defined(__riscos__) || defined(__sun)

# if defined(HAS_UNSETENV)

if (val == NULL) {

(void)unsetenv(nam);