Read one line from stdin.  Break it into keyword value pairs.  Print
them out.  Pairs are separated in standard CGI fashion, by an
ampersand (&).  Keys and values are separated by equals (=).  Spaces
are replaced by plus (+).  Other strange characters are replaced by
their hexidecimal equivalent (%xx).

Hint: The following s/// substitution will be helpful for dealing with
those strange characters.  s/%([\da-f][\da-f])/pack("C",hex($1))/eig;