fix building on threaded or multiplicity interpreter perl,
the bug was introduced by previous commit

src/http/modules/perl/ngx_http_perl_module.c

diff --git a/src/http/modules/perl/ngx_http_perl_module.c b/src/http/modules/perl/ngx_http_perl_module.c
index 6e4c427..248f578 100644
--- a/src/http/modules/perl/ngx_http_perl_module.c
+++ b/src/http/modules/perl/ngx_http_perl_module.c
@@ -1008,10 +1008,21 @@
 static ngx_int_t
 ngx_http_perl_init_worker(ngx_cycle_t *cycle)
 {
+    ngx_http_perl_main_conf_t  *pmcf;
+
+    pmcf = ngx_http_cycle_get_module_main_conf(cycle, ngx_http_perl_module);
+
+    {
+
+    dTHXa(pmcf->perl);
+    PERL_SET_CONTEXT(pmcf->perl);
+
     /* set worker's $$ */
 
     sv_setiv(GvSV(gv_fetchpv("$", TRUE, SVt_PV)), (I32) ngx_pid);
 
+    }
+
     return NGX_OK;
 }