error "An internal pin can only be fed once by ..."

[flizzywine]

When I was writing 'Xor.hdl' ,and try to load and test it, the Hardware emulation report this problem.
I made it to find out about the bug. The reason is .hdl file doesn't allow name containing character '_'.
Hopes it will help someone facing the same problem.

[Edit by admin: corrected error message in subject.]