in reply to Regexp to exclude one IP and get all others?

but I'm not sure how to write the regexp for the second without removing lines for 127.127.1.0.

Just write a regex that's agnostic to the specific IP address, and then a bit of Perl code that checks if the IP address is 127.127.1.0, and if not, performs the substitution.

Perl 6 - links to (nearly) everything that is Perl 6.

In Section Seekers of Perl Wisdom