postgres doesn't detect other end of the unix socket is gone...

It would appear that sometimes, when a disconnect a unix stream
(ie perl DBI) from postgres in a forceful manner (^C), postgres
doesn't appear to notice and keeps processing the transaction
rather than aborting it.

As an example, I currently see the following open files:
postgres postgres   28780    7* unix stream c3653d80 <-> c2d6d7c0
postgres postgres   23751    7* unix stream c2aeda80 <-> c3615540
postgres postgres   12631    7* unix stream c35e3640 <-> c2ac1000
postgres postgres     586    7* unix stream c35ce400
postgres postgres   29011    5* unix stream c2adb900

The last two are:
  586 ?      Ds   0:00.00 postgres: postgres postgres [local] UPDATE
29011 ttyp0- IW   0:00.00 /usr/pkg/bin/postgres -D /home/postgres/db

In this case, it would appear that 586 hasn't noticed anything strange
happening.  Should it have?

Will this problem go away if I use TCP rather than unix streams?

Or is this a bug of the variety that when postgres is deep inside
an UPDATE, doing lots of disk I/O, it never checks to see if it
should abort because the client has gone?

Actually, I can see aborting being a bug too...is there a way to
control the behaviour here?

Darren