Like Writely (and many more), wikiCalc one more step on the road to M*crosoft Office's death by a thousand cuts at the hands of hosted cross platform apps. BTW, don't know why a Perl app without a GUI is Windows only (perhaps Dan was paranoid about having the a sane set of Perl add on modules?)
From About wikiCalc 0.1.:
The wikiCalc program is a web authoring tool that creates normal web pages. It is for creating and maintaining web pages that include data this is more than just unformatted prose, such as schedules, lists, and tables. It combines some of the ease of authoring and multi-person edit ability of a wiki with the familiar formatting and data organizing metaphor of a spreadsheet.