sub hexdump
{
  my $s;
  $_[0] =~ s/\G([\0-\xff]{1,16})/ $s = $1; $s =~ y|\x20-\x7e|.|c; sprintf("%08X  %-50s|%s|\n", $-[0], "@{[unpack q{(H2)8a0(H2)8}, $1]}", $s);/ge;
  return $_[0];
}