sub ParseAChroms
{
     my ($achromref) = @_;
     my (%value);
     foreach (@$achromref)
     {
          my ($prefix, $data) = /^(\S+):\s+(.*)/;
          if (my $pattern = $achrom_prefix{$prefix})
          {
               ($value{lc $prefix}) = $data =~ /^$pattern$/;
          }
     }

     return @data{qw[ type ac_id length
                      chr_num chr_start chr_end
                      bac_start bac_end orient]};
}