How to separate or split strings that are written in one word?

I've tried following the instructions in this post: How to separate or split strings that are written in one word?
But it doesn't seem to work. Mp3tag doesn't like the expression (\1) (\u): I get the message: "Invalid back reference: specified capturing group does not exist. The error occurred while parsing the regular expression: '(>>>HERE>>>\1) (\u)'."
I tried replacing the "1" with the pipe symbol | because I thought is might be a typing error. The expression parses with the pipe symbol, but does nothing.
Please help.
Thanks.

You have to use the letter l (small L) and not the number 1.
The same applies to your choice of the pipe symbol.
This regular expression works as described
$regexp('TagsLikeThese ',(\w|,)(?=\u),$1 $2)
and this one also:
$regexp('TagsLikeThese ',(\l)(\u),$1 $2)

OK. Thanks.
Of course, the u (uppercase) must be balanced by an l (lowercase). I've made the edit, the script parses, but it made no changes.
This is what I'm trying to do: I have, for example, a song TITLE: "DoItAgainVer2". I want it to be: "Do It Again Ver 2". (I understand the digit might be a different problem. Let's ignore it for now.)
How do I do that?
Thanks again.

You have to show, preferably with a screendump, what you are doing.
$regexp('DoItAgainVer2',(\l)(\u),$1 $2)
leads to
Do It Again Ver2

Hi -
Yes, You've solved my problem brilliantly. And I see where I was wrong. Unfortunately, I've haven't describe the task very well. I want to change multiple files like that.


You can probably see what I want.
Thanks again.
L

The expression should work for most of the titles.
Select the files in the files list.
Create an action of the type "Format value" or open the function Convert>Tag-Tag
Select as field: TITLE
Enter as
Format string: $regexp(%title%,(\l)(\u),$1 $2)
Apply the function with OK.

It worked like a charm. Thank you so much!
L

Is there as tutorial here that will help me learn how to write formulas/expressions like
"$regexp(%title%,(\l)(\u),$1 $2)"?
For example, I am familiar with a certain amount of programming, so I get the use of %%, but where are the variables $1 and $2 defined (if they are variables)? And the syntax of the backslashes, etc.
Not asking for that information now, just please point me to where it is.
Thanks.
L

See e.g. the help (press F1)

Or see this forum and the howtos on regular expressions.

This script works really well whenever you're using it in the tag. To tag format. But when you try to use this same exact logic and an action, it does not work correctly. What's the work around to get it to work in an action?

It works in any action that allows a generating format string. The most versatile in this case would be an action of the type "Format value".