{
my %MSISDN=();

#populate the subscription list to hash MSISDN

        open(FILE,"/tmp/subscription_list") || die "Unable to open subscription file";
        sub file_merge(\%MSISDN);
        close(FILE);

my  %Calls=();

#populate the usage types to hash Calls

       open(FILE1,"/tmp/Call_Det")|| die "Unable to open call_details file";
       sub file_merge(\%Calls);
       close(FILE1);
}

sub file_merge(%hash_ref)
{
while (<>) {
  chomp;
  my ($key, @values) = split /-/, $_;
  push @{$hash_ref{$key}}, [ @values ];
}

}