You mean you want to fetch the parameter list as a hash? It's right in the CGI documentation.

Update Ah - now I see, you want to do some "structured" parameters. No, I'm not aware of something like that, but if you go for dots as delimiters, it's fairly easy to write yourself:

my %params = $q->Vars;
my @keys = keys %params;
for my $k (sort @keys) {
    if (/[.]/) {
        my $v = delete $params{ $k };
        my $level = \%params;
        my @items = split /[.]/, $k;
        my $key = pop @items;
        for (@items) {
            $level->{ $_ } ||= {};
            $level = $level->{ $_ };
        };
        $level->{ $key } = $v;
    };
};
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