When trying to match non-latin characters like the Swedish åäö, it seems that -i does not work.
$ cat testfile
$ ack åäö testfile
$ ack Åäö testfile
$ ack -i Åäö testfile
$ ack -i test testfile
This is with App::Ack 1.90 from CPAN on perl 5.10.
Reported in ack2 as petdance/ack2#297.