[TxMt] Invisible characters

Hi all!

I have a problem with invisible characters here. E.g. writing perl code, I use || quite often. I produce this character on my Swiss German keyboard using Option-7. Normally, I put a space after || to increase readability. There it happens that I keep the option key pressed while pressing the space key - and this apparently produces some invisible character. In any case, perl complains:

Unrecognized character \xC2 at /Users/abonhote/test2.pl line 5.

I have turned on "show invisibles", but the extra character doesn't show up. How can I avoid typing these characters?

Thanks in advance!

André