use strict;
use Data::Dumper;

my @fields = qw(cust_id ssn relation);
my @ent = ("A1", "C1", "S1");
my @id  = ("007", "008", "005");
my @ssn = ("999-99-9999", "888-88-8888", "777-77-7777");
my @rel = ("self", "spouse", "son");
my %data;

for my $i (0..$#ent) {
   my %hash;
   @hash{@fields} = ($id[$i],$ssn[$i],$rel[$i]);
   $data{$ent[$i]} = \%hash;   
}

print Dumper \%data;