Shader error: Keyword 'to' or 'rel' expected

For my frag shader:

:gobj(error): created-shader: Keyword ‘to’ or ‘rel’ expected (uniform in float4x4 dlight_dlight)

I’d post the whole shader, but its generated in code and hugely verbose and illegible. (Shader generator progress!)

It works fine for my ambient lights, but dlight does gives this error. I can’t seem to find any info on what the error means or how to fix it. (I have never used ‘to’ or ‘rel’ in a shader, of heard of such a thing)

in uniform float4x4 dlight_dlight_to_model … der_Inputs
Manual page needs a node about what a to keyword means, and that one needs to be used there.

Also, what is ‘rel’ ?