[pari-users] Prepend [pari-users] to subject line?

[Samuel Lelièvre <samuel.lelievre@gmail.com>]

Could the mailing list engine behind pari-users be made
to prepend [pari-users] to the subject line if the subject
does not already contain [pari-users]?

Note: not only "if it does not *start* with [pari-users]",
as nobody wants subject lines to grow to things like:

[pari-users] Re: [pari-users] Re: [pari-users] pari help