Docs of my()

[Ilya Zakharevich <nospam-abuse@ilyaz.org>]

Is there any documentation of how my(…) is actually parsed?  I can see
that
       my([x,y,z]=[3,4,5]);
and
       my(f(x)=x+1);
are actually “fulfilling the ‘best expectations’” — but not
       my(x=y=List());

Thanks,
Ilya