foreach my $arg (@ARGV) 
  {
  if( $arg =~ /^-B(\d+)$/ ) 
    {
    $before = $1;
    }
  elsif ( $before eq '-B' )
    {
    $before = $arg;
    if( $before !~ /^\d+/ ) 
      {
      die "Bad before argument ($before)\n";
      }
    }
  elsif ( $arg eq '-B' )
    {
    $before = $arg;
    }
  }