From @simoncozens

Larry Wall (lists.p5p)​:

It is impossible to know what all the characteristics of the stream are.
The idea of a discipline is that you can swap it in and it will do magic
that the designers of the system never imagined, much like source filters.

This is why I'm worried that what I'm working on may not be sufficiently
generic. I'm persuading myself that UTF-8 is an important enough thing
to special-case and will worry about the genericity later.

No, I'm not, let's be honest. I just need to read some Japanese, and I
can do that now, so I'm happy.

DISC_USER was my idea whereby we could go mental. I was thinking of
adding CVs to marshal input and output, but then it dawned on me that
one might as well use a tied filehandle.

The implementation worry is where to put this stuff. We're rapidly
running out of private flags to pass messages around with file handles
and open statements. I envisage some sort of `discipline magic' but I
don't know how to do it.