#!/usr/bin/perl -wl 
use Data::Dumper;
use CGI;

sub cgi2args {
    my $cgi = shift;
    my $args = {};
    for my $name ($cgi->param) {
        my @vals = $cgi->param($name);
        my $val = @vals == 1 ? $vals[0] : \@vals;
#print "$name $val";
           
        my ($first, @segments) = split /\./, $name;
        my $a = \$args->{$first};
        for (@segments) {
            if(/^(\d+)$/ && $1 < 50) {
                $$a = [] unless defined $$a;
                die "CGI param clash for $name=$_" unless ref $$a eq'A
+RRAY';
                $a = \($$a->[$1]);
            } else { 
                $$a = {} unless defined $$a;
                die "CGI param clash for $name=$_" unless ref $$a eq '
+HASH';
                $a = \($$a->{$_});
            }   
#print "end ",Dumper([$args,$a]);
        }
        die "CGI param clash for $name value $val" if defined $$a;
        $$a = $val;
    }   
    return $args;
}   
$Data::Dumper::Terse = 1;
$Data::Dumper::Indent = 0;
for $q (
            'a.0=3&a.2=4', 
            'a.0=3&a.2=4&b.c.0=x&c=2&c=3&d=',
            # bad ones
            'a.0=3&a.c=4',
            'a.c=3&a.0=4',
            'a.0=3&a=b',
            'a.a=3&a=b',
            'a=3&a.0=b',
            'a=3&a.a=b',
        ) { 
    print "   $q => ", eval { Dumper(cgi2args(CGI->new($q))) } || $@;
}   


__END__
[download]

$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.
[download]