Return an integer from an XSUB immediately. Uses C<XST_mIV>.
=for apidoc Am|void|XSRETURN_NV|NV nv
-Return an double from an XSUB immediately. Uses C<XST_mNV>.
+Return a double from an XSUB immediately. Uses C<XST_mNV>.
=for apidoc Am|void|XSRETURN_PV|char* str
Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.