Hello,
a minimal test case to investigate 1c41f98 that bisect pointed to. Dash
"-" in character [range] is treated literally. The patch is:

-                   if (!in_brace_param)
-                       in_brace_param = bct;
+                   if (!in_brace_param) {
+                       if ((in_brace_param = bct))
+                           seen_brct = 0;
+                   }

The result of script is (first line – not matched, no ^G etc.
replacement):

    this module ^GON-THE-FLY^_, without list restart
    this module ONTHEFLY, without list restart

Script contains alternative [^x-ya] pattern that works (and [^ax-y] that
doesn't).

-- 
  Sebastian Gniazdowski
  psprint3@fastmail.com