use strict;
use warnings;

use CGI;

my $cgi = new CGI;

$cgi->param( 'bla[0]', 'bla[0]' );
$cgi->param( 'bla[1]', 'bla[1]' );
$cgi->param( 'foo[\'bar\']', 'foo[\'bar\']' );
$cgi->param( 'foo[\'baz\']', 'foo[\'baz\']' );

# zum testen
$cgi->param( 'bla[\'bar\']', 'bla[\'bar\']' );
$cgi->param( 'foo[0]', 'foo[0]' );

my %form;

for my $param ( $cgi->param ) {
    my( $name, $index );
    if ( ( $name, $index ) = $param =~ /(\w+)\[(\d+)\]/ ) {
        if ( defined $form{$name} and ref $form{$name} ne 'ARRAY' ) {
            warn "$param tries to overwrite a non-array";
        }
        else {
            $form{$name}->[$index] = $cgi->param( $param );
        }
    }
    elsif ( ( $name, $index ) = $param =~ /(\w+)\[\'(\w+)\'\]/ ) {
        if ( defined $form{$name} and ref $form{$name} ne 'HASH' ) {
            warn "$param tries to overwrite a non-hash";
        }
        else {
            $form{$name}->{$index} = $cgi->param( $param );
        }
    }
    else {
        $form{$param} = $cgi->param( $param );
    }
}

use Data::Dumper;
print Dumper \%form;