Matching partial things with a reversal

[Christopher Browne]

This may be an easy idiom that I'm just not thinking of...

I have cases where I'd like to comment out lines in config files that
_don't_ match the new form.

For instance, I want to configure /etc/postfix/main.cf, and set
various fields to partiuclar values...

main_domain = ( cbbrowne.com )

editfiles:
 { /etc/postfix/main.cf

   AppendIfNoSuchLine "myhostname=$(main_domain)"
   HashCommentLinesContaining "^[^#]*myhostname=(NOT SURE WHAT)"
 }

I'm not sure what regex is going to generally match "anything that's
not $(main_domain)".

Note that this idiom is also going to be real useful for /etc/hosts...
-- 
select 'cbbrowne' || '@' || 'gmail.com';
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