The -e is what tells perl that "this is code, not a filename." One I regularly use (with perl) that doesn't seem to be mentioned yet is -p -i -e to inline modify files line-by-line. This is very nice for global search/replace actions on files found via find, grep or ack.
Yup, -i is very very useful, though I prefer to always call it as -i.bak (=> do the edit in place and make a backup of the original file as "filename.original.bak"), in case I do something hideously wrong.
For what it's worth (you may know this but maybe not everyone does), Ruby also provides the -i flag.
ImportError: No module named wsgi
I updated to 1.4.5 and it worked fine.