diff --git a/c/mapping/context_flags.h b/c/mapping/context_flags.h
index 3aaf9a18b..581428479 100644
--- a/c/mapping/context_flags.h
+++ b/c/mapping/context_flags.h
@@ -5,9 +5,10 @@
 // there, and (b) because we get far better control over error messages here (vs. 'syntax error').
 // The following flags are used as the CST is built from the AST for CST-build-time validation.
 
-#define IN_BINDABLE     0x0100 // boundvars are only OK inside a bindable, e.g. (recursively) inside a for-loop
-#define IN_BREAKABLE    0x0200 // break/continue are only OK (recursively) inside for/while/do-while
-#define IN_BEGIN_OR_END 0x0400 // $stuff is not OK (recursively) inside begin/end
-#define IN_MLR_FILTER   0x0800 // mlr filter takes only a single boolean; no @-vars; no looping; etc.
+#define IN_BINDABLE     0x00000100 // boundvars are only OK inside a bindable, e.g. (recursively) inside a for-loop
+#define IN_BREAKABLE    0x00000200 // break/continue are only OK (recursively) inside for/while/do-while
+#define IN_BEGIN_OR_END 0x00000400 // $stuff is not OK (recursively) inside begin/end
+#define IN_FUNC_DEF     0x00000800 // $stuff, @stuff is not OK inside user-defined functions
+#define IN_MLR_FILTER   0x00004000 // mlr filter takes only a single boolean; no @-vars; no looping; etc.
 
 #endif // CONTEXT_FLAGS_H
diff --git a/c/mapping/mlr_dsl_cst_func_subr.c b/c/mapping/mlr_dsl_cst_func_subr.c
index a5da3e1bd..0d36c4543 100644
--- a/c/mapping/mlr_dsl_cst_func_subr.c
+++ b/c/mapping/mlr_dsl_cst_func_subr.c
@@ -92,7 +92,7 @@ udf_defsite_state_t* mlr_dsl_cst_alloc_udf(mlr_dsl_cst_t* pcst, mlr_dsl_ast_node
 		}
 		sllv_append(pcst_udf_state->pblock_statements,
 			mlr_dsl_cst_alloc_statement(pbody_ast_node, pcst->pfmgr, pcst->psubroutine_states,
-				type_inferencing, context_flags | IN_BINDABLE));
+				type_inferencing, context_flags | IN_BINDABLE | IN_FUNC_DEF));
 	}
 
 	// Callback struct for the function manager to invoke the new function:
diff --git a/c/mapping/rval_expr_evaluators.c b/c/mapping/rval_expr_evaluators.c
index 3aba50d2f..9c02f6746 100644
--- a/c/mapping/rval_expr_evaluators.c
+++ b/c/mapping/rval_expr_evaluators.c
@@ -23,12 +23,11 @@
 rval_evaluator_t* rval_evaluator_alloc_from_ast(mlr_dsl_ast_node_t* pnode, fmgr_t* pfmgr,
 	int type_inferencing, int context_flags)
 {
-	// xxx split out helper methods for outer if-statement.
-	// xxx convert innner if-elses to switches.
 	//  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 	if (pnode->pchildren == NULL) {
 		// leaf node
 		switch(pnode->type) {
+
 		case MD_AST_NODE_TYPE_FIELD_NAME:
 			if (context_flags & IN_BEGIN_OR_END) {
 				fprintf(stderr, "%s: statements involving $-variables are not valid within begin or end blocks.\n",
@@ -37,6 +36,7 @@ rval_evaluator_t* rval_evaluator_alloc_from_ast(mlr_dsl_ast_node_t* pnode, fmgr_
 			}
 			return rval_evaluator_alloc_from_field_name(pnode->text, type_inferencing);
 			break;
+
 		case MD_AST_NODE_TYPE_STRNUM_LITERAL:
 			return rval_evaluator_alloc_from_strnum_literal(pnode->text, type_inferencing);
 			break;
diff --git a/c/reg_test/dev b/c/reg_test/dev
index 907bd1372..279b0083b 100755
--- a/c/reg_test/dev
+++ b/c/reg_test/dev
@@ -75,88 +75,42 @@ run_mlr() {
 	num_passed=`expr $num_passed + 1`
 }
 
+mlr_expect_fail() {
+  # Use just "mlr" for info messages
+	echo mlr "$@"
+	echo mlr "$@" >> $outfile
+  # Use path to mlr for invoking the command
+    set +e
+	$path_to_mlr "$@" >> $outfile 2>&1
+    status=$?
+    if [ $status -ne 1 ]; then
+        echo "Exit status was $status; expected 1."
+        echo "Exit status was $status; expected 1." >> $outfile
+    fi
+    set -e
+	echo >> $outfile
+    test $status -eq 1
+	# since set -e
+	num_passed=`expr $num_passed + 1`
+}
+
 # ================================================================
-announce GRAMMAR REORG
+announce FUNC PROHIBITS
 
-run_mlr -n put -v '$["x"]=3'
-run_mlr -n put -v '@["x"]=3'
-run_mlr -n put -v '$[$y]=$y'
-run_mlr -n put -v '@[@y]=@y'
-
-run_mlr -n put -v '@x=2; @x["y"]=3; @x["y"][$z]=4'
-run_mlr -n put -v '@["x"]=2; @["x"]["y"]=3; @["x"]["y"][$z]=4'
-run_mlr --from $indir/abixy put -q -v '@a=2; @b["y"]=3; @c["y"][$a]=4; emitp all'
-run_mlr --from $indir/abixy put -q -v '@a=2; @b["y"]=3; @c["y"][$a]=4; emitp all'
-run_mlr --from $indir/abixy put -q -v '@["a"]=2; @["b"]["y"]=3; @["c"]["y"][$a]=4; emitp all'
-
-echo x=1|mlr put '$x=$x+1; for (k,v in $*) { $[v] = typeof(v)}'
-# x=2,2=MT_INT
-
-echo x=1|mlr put 'for (k,v in $*) { $[v] = typeof(v)}'
-# x=1,1=MT_STRING
-
-run_mlr put -v '@s = NR; $t = typeof(@s); $u= typeof(@["s"]); emitp all' $indir/abixy
-
-run_mlr --opprint put -v '@s = NR; $t = @s; $u=@["s"]' $indir/abixy
-
-run_mlr put -v '@t["u"] = NR; $tu = @["t"]["u"]; emitp all' $indir/abixy
-
-run_mlr put -v '@["t"]["u"] = $y; emitp all' $indir/abixy
-
-run_mlr --from $indir/abixy put -v '$sum = 0; for(k,v in $*) {if (k =~ "^[xy]$") {$sum += $[k]} }'
-
-run_mlr --from $indir/abixy -n put -v '
-  $a = @s;
-  $b = @t[1];
-  $c = @u[1][2];
-  $d = @v[1][2][3];
-  $e = @["s"];
-  $f = @["t"][1];
-  $g = @["u"][1][2];
-  $h = @["v"][1][2][3];
-'
-
-run_mlr -n put -v 'emit  @*'
-run_mlr -n put -v 'emitp @*'
-run_mlr -n put -v 'unset @*'
-
-run_mlr --opprint --from $indir/abixy put -q -v '
-  for (k,v in $*) {
-      @logging1[NR][k] = v;
-      if (k == "x") {
-          break;
-      }
-  }
-
-  for (k,v in $*) {
-      if (k == "x") {
-          break;
-      }
-      @logging2[NR][k] = v;
-  }
-
-  for (k,v in $*) {
-      @logging3[NR][k] = v;
-      if (k == "x") {
-          continue;
-      }
-  }
-
-  for (k,v in $*) {
-      if (k == "x") {
-          continue;
-      }
-      @logging4[NR][k] = v;
-  }
-
-  end {
-    emitp @logging1, "NR", "k";
-    emitp @logging2, "NR", "k";
-    emitp @logging3, "NR", "k";
-    emitp @logging4, "NR", "k"
+mlr_expect_fail --from $indir/abixy put '
+  func f(x,y,z) {
+    return $a # cannot reference srecs from functions
   }
 '
 
+mlr_expect_fail --from $indir/abixy put '
+  func f(x,y,z) {
+    return $[x] # cannot reference srecs from functions
+  }
+'
+
+run_mlr -n put ''
+
 # ================================================================
 cat $outfile
 
diff --git a/c/reg_test/run b/c/reg_test/run
index 862368ce0..4cecf6fe0 100755
--- a/c/reg_test/run
+++ b/c/reg_test/run
@@ -4707,12 +4707,10 @@ run_mlr --opprint --from $indir/abixy filter -f $indir/filter-script-piece-1 -f
 echo
 echo ================================================================
 echo "Differences between $expfile and $outfile:"
-echo
-
 diff -I '^mlr ' -C5 $expfile $outfile
-
 echo "No differences found between $expfile and $outfile" # since set -e
 echo ================================================================
+echo
 
 # ================================================================
 echo ALL REGRESSION TESTS PASSED
diff --git a/c/todo.txt b/c/todo.txt
index 424727b54..272540fc7 100644
--- a/c/todo.txt
+++ b/c/todo.txt
@@ -24,8 +24,8 @@ UDFs:
     - (lhs) no subr call
     - (lhs) no srec assignment x 3, no oosvar assignment x 2, no filter, no unset
     - (lhs) no tee, emitfx3; but allow print; ?dump?
-    - (rhs) no srec/oosvar references
 * kw autodoc mods for func/subr/call/return; also add NR PI E etc. to keyword help.
+* disallow func/subr redefines
 * xxxes
 * xxxes in reg_test/run
 * valgrinds