Starting out on Perl I am reading this code for obtaining params from a http request: 
1. read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
2. @pairs = split(/&/, $buffer);
3. foreach $pair (@pairs) {
4.      ($name, $value) = split(/=/, $pair);
5.      $value =~ tr/+/ /;
6.      $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
7.      $value =~ s/\s/ /g;
8.      $value =~ s/<([^>]|\n)*>//g;
9.      $value =~ s/<//g;
10.     $value =~ s/>//g;
11.     $FORM{$name} = $value;
12.}

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Lines 1-4 I understand. I tried to look up the tr in line 5 in some documentation. It stated that tr/// is a translator and identical to y///. Looking up y/// I was informed that it is identical to tr///. For a novice this doesn't add much clarity ;-) Could somebody please explain what is going on in lines 5-11, i.e. what is the purpose of each of the patterns? I've figured out that that pack-thing in line 6 creates some sort of binary structure, but what info does it contain and whats's the purpose? What are the origins of the $FORM variable? Any answers will be gratefully accepted :-)

In reply to Explanation of regexps for obtaining POST params by r_ibsen

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