+params (required) - Hashref of keys and values, often passed as
+C<scalar($cgi->Vars)> from a form. This will be scanned for keys of the form
+"pkeyNN" (where pkey is the primary key column name, and NN is an integer).
+Each of these designates one record in the "many" table. The contents of
+that record will be taken from other parameters with the names
+"pkeyNN_myfield" (where myfield is one of the fields in the 'fields'
+array).