Matching with exclusion?

[Benoit Lefebvre]

We have a software here that do a regex check for the usernames that
runs it.

All our usernames are as following: A letter followed by a set of 5
numbers.

Currently, in the config we have a line like that:

^a[0-9]{5}$

To specify that every users starting with the letter "a" can run it.

We are having an issue with one user (a34882) and we want to exclude
him

Unfortunately the software was not designed with an exclusion list

How can I add the username in the regexp that match the users to
exclude a34882 ?

Thanks,
--Ben

[ThomasW]

I have a similar problem and found (?!...) does the job ("..." is the
expression to be excluded).

Thomas W.

[Benoit Lefebvre]

The application uses pcre, this is not working.

I tested the ?! with perl it's fine but pcre don't seems to be liking
that

any other solutions? Editing the program is not an option right now

Thanks,
--Ben