Do you mean something along the lines of:
die "You are socketless!\n"
unless Config::config_vars(qw/d_socket/) eq 'define';
If you need really specific socket capabilities there is any number of fine-grained tests you could perform. Randomly cutting and pasting from perldoc Config gives things like
This variable conditionally defines the
`HAS_GETSERVBYNAME' symbol, which indicates to the C
program that the getservbyname() routine is available to
look up services by their name.
Is this what you were looking for?
g r i n d e r