If in doubt, default to the old MS-DOS (CP/M) file names (which seem to work in almost all cases)...

Rules...

(1) No more than 8 Characters (only Alphabetics, Numerics and Hyphen allowed)
(2) No Spaces
(3) No Hieroglyphics ie Ampersands (&), Asterisks (*), Commas, Full-Stops, Percents (%) or anything else - as many had special meanings within the File, Directory or Search System.
(4) You could have a Full-Stop (Period) and you could then follow that with an extension of up to three characters (in our case it's .BAS or .LST or .HEX etc)

All of which leads me to suspect that the PICBasic Command Line Parser has it's roots further back than you might think.

...and before anybody gets any strange ideas about my age... my Dad brought home an old Heath/Zenith Z89 from a local junk shop to play with one day when I was a kid... thought I might learn something... yeah... I learnt about Hard Sectored Floppy Disks with a 102kb capacity and an operating system called HDOS - real useful!