sub hexdump($data) {
  $data =~ s/\G(.{1,16})(\1+)?/
    sprintf "%08X  %-50s|%s|\n%s",
        $-[0],
        "@{[unpack q{(H2)8a0(H2)8},$1]}",
        $1 =~ y{ -~}{.}cr,
        "*\n"x!!$+[2]
  /segr . sprintf "%08X", $+[0]
}