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;
}