Interesting, I remember a kernel issue being one of the possible causes I had on my list, and I forget what exactly led me to consider that, but I never got as far as playing with kernel upgrades on this box.
I fixed the issue I was having by downgrading to Want-0.07.
Robin helpfully provided me with a link:
http://backpan.perl.org/authors/id/R/RO/ROBIN/Want-0.07.tar.gz
I have also now tried the newer Want-0.10 and it has the same issue as Want-0.09:
*** glibc detected *** corrupted double-linked list: 0x0aed9788 ***
[Thu Mar 30 10:49:36 2006] [notice] child pid 19739 exit signal Aborted (6)