Perl: added PERL_SET_INTERP(). For Perl compiled with threads, without PERL_SET_INTERP() the PL_curinterp remains set to the first interpreter created (that is, one created at original start). As a result after a reload Perl thinks that operations are done withing a thread, and, most notably, denies to change environment. For example, the following code properly works on original start, but fails after a reload: perl 'sub { my $r = shift; $r->send_http_header("text/plain"); $ENV{TZ} = "UTC"; $r->print("tz: " . $ENV{TZ} . " (localtime " . (localtime()) . ")\n"); $ENV{TZ} = "Europe/Moscow"; $r->print("tz: " . $ENV{TZ} . " (localtime " . (localtime()) . ")\n"); return OK; }'; To fix this, PERL_SET_INTERP() added anywhere where PERL_SET_CONTEXT() was previously used. Note that PERL_SET_INTERP() doesn't seem to be documented anywhere. Yet it is used in some other software, and also seems to be the only solution possible.