$perl -w a 
   a.0=3&a.2=4 => {'a' => ['3',undef,'4']}
   a.0=3&a.2=4&b.c.0=x&c=2&c=3&d= => 
     {'a' => ['3',undef,'4'],
      'b' => {'c' => ['x']},
      'c' => ['2','3'],
      'd' => ''}
   a.0=3&a.c=4 => CGI param clash for a.c=c at a line 22.
   a.c=3&a.0=4 => CGI param clash for a.0=0 at a line 18.
   a.0=3&a=b => CGI param clash for a value b at a line 27.
   a.a=3&a=b => CGI param clash for a value b at a line 27.
   a=3&a.0=b => CGI param clash for a.0=0 at a line 18.
   a=3&a.a=b => CGI param clash for a.a=a at a line 22.