diff -ur brlcad-7.4.2.old brlcad-7.4.2
diff -ur brlcad-7.4.2.old/configure.ac brlcad-7.4.2/configure.ac
--- brlcad-7.4.2.old/configure.ac	2005-08-16 23:15:20.000000000 +0200
+++ brlcad-7.4.2/configure.ac	2005-09-04 21:49:26.000000000 +0200
@@ -149,7 +149,7 @@
 # set up our default shared/non-shared data install directories
 #         e.g. /usr/local/share/brlcad/7.4.0
 AC_MSG_CHECKING([where BRL-CAD resources are to be installed])
-if test "x$datadir" = "x\${prefix}/share" ; then
+if test "x$datadir" = "x${prefix}/share" ; then
 	bc_data_dir="${bc_prefix}/share/brlcad/${BRLCAD_VERSION}"
 else
 	# allow a complete override
@@ -1826,9 +1826,8 @@
 	LIBS="$LIBS $LIBTK $LIBTCL"
 fi
 AC_TRY_RUN([
-#ifdef HAVE_TK_H
+#  include <tcl.h>
 #  include <tk.h>
-#endif
 #ifndef TK_MAJOR_VERSION
 #  error Unknown major version of Tk
 #endif
@@ -1884,7 +1883,6 @@
 		fi
 	fi
 fi
-build_brlcad_tk=yes
 AC_MSG_CHECKING(whether to build Tk)
 dnl Need to update version number(s) in src/other/libtk/Makefile.am too
 TK_VERSION="8.4"
@@ -1993,17 +1991,15 @@
 dnl this test is probably not sufficient if iwidgets is not locateable
 dnl in the tcl auto_path.
 AC_TRY_RUN([
-#ifdef HAVE_TCL_H
 #  include <tcl.h>
-#endif
 int main() {
     Tcl_Interp *interp;
-    const char *cmd = "package require iwidgets";
+    const char *cmd = "package require Iwidgets";
     interp = Tcl_CreateInterp();
-    if (Itcl_Init(interp) == TCL_ERROR) {
+    if (Tcl_Init(interp) == TCL_ERROR) {
 	return 1;
     }
-    if (Tcl_Eval(interp, cmd) != TCL_OK || interp->result[0] != '\0') {
+    if (Tcl_Eval(interp, cmd) != TCL_OK || interp->result[0] == '\0') {
 	return 1;
     }
     return 0;