in reply to On zero-width negative lookahead assertions
The following works if you break it into two expressions, but I can't see why yours doesn't match.
Update: Moving it around also works:perl -ne '/^root:\s*/ and $_ !~ /admin\@somewhere\.here/ and print' +alias
perl -ne '/^root:(?!\s*admin\@somewhere\.here)/ and print' alias
pbeckingham - typist, perishable vertebrate.