FAQ 9.10 How do I decode or create those %-encodings on the web?

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9.10: How do I decode or create those %-encodings on the web?

    (contributed by brian d foy)

    Those "%" encodings handle reserved characters in URIs, as described in
    RFC 2396, Section 2. This encoding replaces the reserved character with
    the hexadecimal representation of the character's number from the
    US-ASCII table. For instance, a colon, ":", becomes %3A.

    In CGI scripts, you don't have to worry about decoding URIs if you are
    using "CGI.pm". You shouldn't have to process the URI yourself, either
    on the way in or the way out.

    If you have to encode a string yourself, remember that you should never
    try to encode an already-composed URI. You need to escape the components
    separately then put them together. To encode a string, you can use the
    the "URI::Escape" module. The "uri_escape" function returns the escaped

            my $original = "Colon : Hash # Percent %";

            my $escaped = uri_escape( $original )

            print "$string\n"; # 'Colon%20%3A%20Hash%20%23%20Percent%20%25%20'

    To decode the string, use the "uri_unescape" function:

            my $unescaped = uri_unescape( $escaped );

            print $unescaped; # back to original

    If you wanted to do it yourself, you simply need to replace the reserved
    characters with their encodings. A global substitution is one way to do

            # encode
            $string =~ s/([^^A-Za-z0-9\-_.!~*'()])/ sprintf "%%%0x", ord $1 /eg;

            $string =~ s/%([A-Fa-f\d])/chr hex $1/eg;


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