I printed the value of `[get_ports clk_74a]` and it turned out to be "_col0"
(Wasn't sure how types worked in this context so I tried, and got the same for, `[join [get_ports clk_74a] "///"]`)
This causes `create_generated_clock` to give the error "-master_clock must contain exactly one valid clock."
I am PRETTY sure this means I have bumped up against the edge of how far I can go and I should abandon the attempt to use `create_generated_clock` and just use a PLL

(I do notice if I google _col0 I find this is a generic name for, if something wants to return a "collection" (this is a Synopsis data type that is like a fancy list), a collection is instantiated and its name is returned and this is usually _col0. But none of the things I find claimed to be ways of interacting with a collection— get_object_name, foreach_in_collection— appears to do anything, either it's returning an empty string or it's causing the whole thing to error-and-abort and I don't know where to find the error message.)