Well I have installed several more Tk modules, the GD module, and libgd 2.0.15 to get this working, and it still doesn't. That's enough messing around for me for one day, anyhow. Yes, there is a down side to having hundereds of independently created modules available. Anyhow, here is where I gave up:

GD.xs: In function `newDynamicCtx': (and numerous other functions)
GD.xs:430: structure has no member named `gd_free'