diff -up asymptote-2.81/configure.ac.libtirpc asymptote-2.81/configure.ac
--- asymptote-2.81/configure.ac.libtirpc	2022-06-01 16:58:58.770519207 -0400
+++ asymptote-2.81/configure.ac	2022-06-01 17:00:46.644262786 -0400
@@ -405,6 +405,17 @@ case "$OSTYPE" in
      ;;
 esac
 
+PKG_PROG_PKG_CONFIG([0.9.0])
+AS_IF(
+  [test "$enable_tirpc" != "no"],
+  [PKG_CHECK_MODULES([TIRPC], [libtirpc >= 0.2.4],
+                    [LIBS="${LIBS} ${TIRPC_LIBS} "
+                     CPPFLAGS="${CPPFLAGS} ${TIRPC_CFLAGS} "
+                     AC_DEFINE([HAVE_LIBTIRPC], [1],
+                               [Define to 1 if you have and wish to use libtirpc.])],
+                    [AS_IF([test "$enable_tirpc" != "no"], [AC_MSG_ERROR([libtirpc not found.])],
+                           [LIBTIRPC=""])])])
+
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include "xstream.h"])],
                    [AC_SEARCH_LIBS([xdrstdio_create],[nsl tirpc])
                     AC_DEFINE(HAVE_RPC_RPC_H,1,
