Bash extglob pattern with comma

Question

Suppose extglob is turned on in Bash (I use 5.0.11(1)-release (x86_64-apple-darwin18.6.0)) and we have a file with the name list89988777,,,,,+--.txt. I cannot get a , to work in extglob pattern with [...] unless I escape not just the comma but all that goes with it if the , is the first in a [..], which does not make sense to me. Hence:

ls *+([[:digit:]]|[\,\-\+]).txt works, so does

ls *+([[:digit:]]|[[:punct:]]|[-\,+]).txt as well as

ls *+([[:digit:]]|[[:punct:]]|[-+\,]).txt

but

ls *+([[:digit:]]|[\,-+]).txt does not work.

Problem can be solved with ls *+([[:digit:]]|[[:punct:]]|[-+]).txt, which works, or for that matter with ls *+([[:digit:]]|[[:punct:]]|[,-+]).txt which also works. But why is escaping , and all the other chars in a [...] necessary if the first char is a ,?

Answer 1

Credit goes to the user who answered the question in a comment (but then the comment vanished).

It is not the , but actually the - within [...] that causes the problem because it creates a range. Hence, escaping , is not necessary, we just need to make sure the - is first or last in the set.