However, accessing a DOS formatted flash drive, either via compact flash or SMC, is availible.

There is existing code to read Memopad files, "schlep'ed" files (normal files wrapped around Palm's pdb database format...) and PilotDOC format.

But for a cheap (read: not free) scripting enviroment, you should look into PocketC http://www.orbworks.com. The only downside is that it doesn't have Internet connectivity, but thankfully is extendable.

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$Stalag99{"URL"}="http://stalag99.keenspace.com";

If by a filesystem you mean a directory system for perl to live in. I don't know about the other stuff, but this just struck me....
After looking at this page I had an idea. If there is a version of zlib for PalmOS and zip files can have filesystems (or at least directory structures) so why not have a PalmOS app that calls the zlib to dynamically unzip what you need, this would cut down on the physicaly space need for perl (but increasing the swapping needed in RAM, bite me).

I have no idea at all how you would implement this, but it would be cool if it worked :)

I know that Plucker, a perl app, uses zlib on the palm to load web pages downloaded from you PC.

The Evil but Fickle Dr Lambado
In the Kingdom of the Blind, the One Eyed Man is King

Aside from that, I can see cases where it might make sense to have Perl (in some form) available on the Palm. Your comment about "Perl-like" may be right on the money; for instance, imagine a byte-code interpreter that lacks string eval (and hence the compiler and its huge tables). This could work like a cross-compiler; you'd spit out bytecodes into a .PDB file, and there could be a minimal Perl VM in a .PRC that could interpret the bytecodes.

As long as you don't use string eval (and this would rule out, for instance, having a Perl compiler or full-featured debugger that actually ran on the Palm), this might be a good way for Perl-fluent programmers to make Palm apps — when loaded with Palm-specific Perl modules so you can do something useful with the Palm databases, inter-process communication, and events.

Much as I'd like to see a real language environment that I could program on the Palm (perhaps with an attached keyboard), having a quick way to knock off Palm apps would be a real win.

Then how does it store the add-on programs, text files and graphics, and all the stuff the PDA app uses?

It needs some way to organize and find it again.

It only has "databases", which are accessed record by record (as opposed to the Unix byte-stream model). I suppose you could use one of these to emulate files, but it wouldn't interact with anything, and so would not be useful.

To make a Palm language useful, you have to provide access to the databases (as records, not as bytes). And ideally, you'd have some GUI layer so that you could interact and respond to the many PalmOS events (like being put to sleep).