I find IPC::Shareable extermely handy. Very frequently I want programs to be able to exchange some pieces amounts of data; and I want them to do it quickly. Files are too slow and "real" TCP/IP networking can be a hastle for just sharing a little data. Also when the processes aren't related (i.e. they wouldn't fork to create each other under the processes model ; they wouldn't be separate threads under the therading model) it is just really handy to use IPC::Shareable.

Its just that so many people think its either "pipes or TCP/IP" when their processes need to communicate. SysV IPC is extremely apropriate for some problems.