Mass regex search-and-replace BETWEEN patterns - regex

Question

I have a directory with a bunch of text files, all of which follow this structure:
...
- Some random number of list items of random text
- And even more of it
PATTERN_A (surrounded by empty lines)
- Again, some list items of random text
- Which does look similar as the first batch
PATTERN_B (surrounded by empty lines)
- And even more some random text
....
And I need to run a replace operation (let's say, I need to prepend CCC at the beginning of the line, just after the dash) on only those "list items", which are between PATTERN_A and PATTERN_B. The problem is they aren't really much different from the text above PATTERN_A, or below PATTERN_B, so an ordinary regex can't really catch them without also affecting the remaining text.
So, my question would be, what tool and what regex should I use to perform that replacement?
(Just in case, I'm fine with Vim, and I can collect those files in a QuickFix for a further :cdo, for example. I'm not that good with awk, unfortunately, and absolutely bad with Perl :))
Thanks!

Answer 1

If I have understood your questions, you can do so quite easily with a pattern-range selection and the general substitution form with sed (stream editor). For example, in your case:
$ sed '/PATTERN_A/,/PATTERN_B/s/^\([ ]*-\)/\1CCC/' file
- Some random number of list items of random text
- And even more of it
PATTERN_A (surrounded by empty lines)
-CCC Again, some list items of random text
-CCC Which does look similar as the first batch
PATTERN_B (surrounded by empty lines)
- And even more some random text
(note: to substitute in place within the file add the -i option, and to create a backup of the original add -i.bak which will save the original file as file.bak)
Explanation
/PATTERN_A/,/PATTERN_B/ - select lines between PATTERN_A and PATTERN_B
s/^\([ ]*-\)/\1CCC/ - substitute (general form 's/find/replace/') where find is from beginning of line ^ capturing text between \(...\) that contains [ ]*- (any number of spaces and a hyphen) and then replace with \1 (called a backreference that contains all characters you captured with the capture group \(...\)) and appending CCC to its end.
Look things over and let me know if you have questions or if I misinterpreted your question.

Answer 2

With Perl also, you can get the results
> perl -pe ' { s/^(\s*-)/\1CCC/g if /PATTERN_A/../PATTERN_B/ } ' mass_replace.txt
...
- Some random number of list items of random text
- And even more of it
PATTERN_A (surrounded by empty lines)
-CCC Again, some list items of random text
-CCC Which does look similar as the first batch
PATTERN_B (surrounded by empty lines)
- And even more some random text
....
>