Name of files causes error. Why?

[Xan]

Hi,

With helloworld program named with score or underscore, I receive 
the following __annoying__ error:

$ gdmd-4.6 hola-temp.d
hola-temp.d: Error: module hola-temp has non-identifier 
characters in filename, use module declaration instead

Why?
Can someone fix it. It's really annoying

Thanks in advance,
Xan.