[Dovecot] sieve filtering, rewriting subjects

[Ian P. Christian]

Is it possible to modify an emails subject line in a sieve script?

I've seen references to 'addtag' whilst googling, but it appears
dovecots implementation doens't support it - are there any other methods?

As a side note, can anyone suggest a web based script editor that works?
Simply a text area to write the script in would do

Thanks,

-- 

Ian P. Christian ~ pookey.co.uk