If you are a tourist in the code base, do the least intrusive thing possible. Definitely stick to any explicit or implicit coding standard.

If you have inherited a code base, you will gradually get to know it. After a while you know the code well enough to form a vision of your own on how things should be, and molding the software to that vision can actually be rewarding since you get to see steady progress as you fix things.

The book Perl Medic is an excellent read.

/J