Fix error message for undefined vars

src/compile.c

@@ -1007,6 +1007,8 @@ static int expand_call_arglist(block* b) {
       if (!curr->bound_by) {
         if (curr->symbol[0] == '*' && curr->symbol[1] >= '1' && curr->symbol[1] <= '3' && curr->symbol[2] == '\0')
           locfile_locate(curr->locfile, curr->source, "jq: error: break used outside labeled control structure");
+        else if (curr->op == LOADV)
+          locfile_locate(curr->locfile, curr->source, "jq: error: $%s is not defined", curr->symbol);
         else
           locfile_locate(curr->locfile, curr->source, "jq: error: %s/%d is not defined", curr->symbol, block_count_actuals(curr->arglist));
         errors++;

tests/jq.test

@@ -278,7 +278,7 @@ null
 
 %%FAIL
 . as $foo | break $foo
-jq: error: *label-foo/0 is not defined at <top-level>, line 1:
+jq: error: $*label-foo is not defined at <top-level>, line 1:
 
 [.[]|[.,1]|until(.[0] < 1; [.[0] - 1, .[1] * .[0]])|.[1]]
 [1,2,3,4,5]