Not a solution, but quoth perldiag:

       panic: utf16_to_utf8: odd bytelen
           (P) Something tried to call utf16_to_utf8 with an odd (as opposed
           to even) byte length.

So somehow you've got Perl thinking your text is UTF16 encoded (two octets per character) but it's got an odd number of bytes to work with (5 in this case). Perhaps your editor's inserting a specious BOM or something that's confuzzling Perl? (Disclaimer: I don't really have any experience with non-ASCII encodings, so take that for what it is (a literal reading of the error message text))

What editor are you using?

AFAICS it shouldn't happen, that is: you shouldn't get into unicode trouble unless you explicitly ask for it. But then this may depend on you perl version (under some osen/environments). Isn't it by any chance 5.8.0?

If you just do this at the shell command line, I expect that you won't get an error:

perl -le 'print "hello, world!"'
[download]

So the question is, what does your "test.pl" do besides that? No solution to your problem, until you show us more info (or figure it out on your own).