-UHAS_STRTOD -Ud_strtod -A undef:HAS_STRTOD -A undef:d_strtod

I tried the first of those shortly after posting. I figured it was a punt worth trying - which it would have been, had it worked ;-)
Thanks for trying out those other arguments, too.

I'm thinking it might require an alteration to Config_h.SH, which is a generated file that ships with the source. However, I don't know how to correctly implement the required changes.
Anyway, my main interest is in ascertaining whether it can be achieved by providing appropriate args to "sh Configure".
I'll ask about it on the perl porters mailing list if nothing turns up here.

Cheers,
Rob