## convert non printable chars to '.' for a string
sub printablestr {
    my $str = shift;
    $str =~ s/[^\x20-\x7f]/./g;
    return $str;
}

## hex dump utility function
sub hd {
  my(@retList, $len, $width, $i, $str);
  $width = $ENV{HEXDUMP_WIDTH} || 16;
  $i = 0;
  $str = '';

  foreach( @_ ) {
    while( my $str = substr($_, $width*$i, $width) ){
      $len = length($str);
      push @retList,
        sprintf("%04X  ".('%02X ' x $len ).('   'x($width - $len))."  
+%s\n",
                $width*$i++, map({ord} split//, $str), printablestr($s
+tr));
      last if $len < $width;
    }
}

return $retList[0] unless wantarray;
return @retList;
}
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