Programming :: Modify Lines That Are Too Long?

I have a CDL netlist with 5630 lines. 512 of the lines are over 128 characters. The tool I am using to read in the CDL returns an error for each line over 128 characters.

If the line is too long I can fix it by adding a line continuation symbol, in this case a "/", somewhere prior to the 128th character then a line feed, obviously, and a "+" to the continuation.

example (pretend its a long line);
before;
this line is too long
after;
this line /
+ is too long

Part of the problem is that I can't use a constant point prior to the 128th character because I can't break up a term.

bad;
this line i /
+ s too long

If I can replace the last space before the 128th character with " / + " on all lines that are over 128 characters then I'm golden. I'm not sure if I need to escape the + or not. If so then the substitution is " / + ". And if I use sed then I'll escape the .