Need help understanding some code ...

[Perobl]

I have been asked to update a script that I did not write. The script is for form processing and the section I'm sharing is basically used to evaluate user data submitted as key-value pairs. I'm having trouble seeing any tangible purpose in four lines of code below (where $value is evaluated):

read (STDIN, $temp, $ENV{'CONTENT_LENGTH'});
@pairs = split(/&/, $temp);
foreach $item(@pairs) {
      ($key, $value) = split(/=/, $item, 2);
        $value =~ tr/+/ /;
        $value =~ s/%(..)/pack("c", hex($1))/ge;
        $value =~ s/\t/ /g;
        $value =~ s/\0//g;
}

I understand what each line does ... for example ...

$value =~ tr/+/ /;

performs transliteration on $value and thus translates characters like !, @, #, etc. to their hex equivalents ... that is, # becomes %23.

$value =~ s/%(..)/pack("c", hex($1))/ge;

The line above then takes the two "hex" digits that make up the string and packs them into their hex equivalent.

$value =~ s/\t/ /g;

This code removes tabs?

$value =~ s/\0//g;

And this code removes nulls? I'm missing the point of these four lines of code used together. It doesn't seem like they're really protecting anything??? Am I missing something? Thanks for your help!