in reply to Pattern matching

The way to say that you don't want something is using a negative lookahead assertion which is (?!...). In your case it'll be

m[ng/(?!2\.0)]

Related documents:
perlre - Perl regular expressions
perlrequick - Perl regular expressions quick start
perlretut - Perl regular expressions tutorial

Hope this helps,
ihb

See perltoc if you don't know which perldoc to read!
Read argumentation in its context!