It seems to me that the whole idea behind Perl is to give programmers freedom to choose what they want - and to skip what they don't. I encounter the "unless" construct often enough, and it doesn't create problems for me. I don't use it, though - I prefer if-then-else, probably because of the languages I first learned had nothing else.

I don't have any great objection to introducing an "otherwise" into Perl, except that there doesn't seem to be any crying need for it. If it does become part of the language I probably won't use it, either - but it wouldn't be difficult to add one more word to the vocabulary of terms I need to understand.