SWISH::3 0.08_04 is passing all tests all over the CPAN testers universe, so that is encouraging.
However, some reports (notably on FreeBSD) report false failures because of a Wstat issue.
I’ve posted about it at PerlMonks and hope someone out there has an easy fix.
Update: finally found a fix for this. The problem is that Perl has its own my_setenv() function that interferes with the native setenv() called by libswish3.c. The fix was to set the magic Perl var PL_use_safe_putenv as shown here. This took many hours and googling to track down. Glad to be done with it (I hope!).