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

##</code><code>##

sub file_merge {
  my $filename = shift;

  open my $fh, '<', $filename
    or die "$filename: $!\n;

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

  return %hash;
}

##</code><code>##

my %msisdn = file_merge('/tmp/subscription_list');
my %calls  = file_merge('/tmp/Call_Det');