The more intersting question is why you think that's strange, given that you aren't using your own name. I use my name just about everywhere (that lets me) instead of a "screen name", and yet I'm the one who's made the odd choice. :)
First things first: I'm sorry. My initial intention wasn't offend you, in any way. I was just curious because you signed a book using some kind of a nickname, and this is not something usual. People use to sign books using his/her names, it doesn't matter how hard is to spell or pronunce it. This is kind of a social convention I'm used to.
What I and my friend noticed yesterday was that you doesn't follow those conventions. Maybe I have expressed myself badly, but the curiosity that I felt at the moment was true. As you're a perl author, I tought that you should be a resonable motivation to use this format for spell your own name.
About not using my own name here: you right, it seems that my behavior is the odd one ;-). But even I have a reason for this: since my university days, its easy to identify me as "Monsieur Champs" than as "Luis Motta Campos" (yeah, this is my real name). That have something to do wth some french-speaking canadian researcher that I supported at LSI, and that translated (!) my last name for their own use.