We should aim to get rid of these warnings:

Argument "\x

" isn't numeric in addition at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/ControllerBase/WS/1.pm line 74.
Use of uninitialized value in hash element at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Edit/Release/Create.pm line 93.
Use of uninitialized value in numeric eq (==) at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Controller/WS/1/Artist.pm line 64.
Use of uninitialized value in string eq at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Controller/Search.pm line 14.
Use of uninitialized value $limit in multiplication at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Data/Search.pm line 487.
Use of uninitialized value $limit in sprintf at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Data/Search.pm line 506.
Use of uninitialized value in concatenation (.) or string at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/WebService/XMLSerializerV1.pm line 60.
[info] Found version 2 format cookie
[error] Invalid cookie sha1 at /home/musicbrainz/musicbrainz-server/script/../lib/MusicBrainz/Server/Controller/User.pm line 145.

There will be more, but these are accounting for the majority of warnings right now.