Im new to Apache::Request myself, so take this with a pinch of salt...

Have you looked at Apache::Table? It provides similar functionality:

        my $q = Apache::Request->new(shift);
        my $table = $q->parms;
        $table->clear;
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You could create an Apache::Request subclass with CGI.pm's full API, eg

package CGIRequest;
use base Apache::Request;

sub new
{
    my $class = shift;
    return bless Apache::Request->new(@_), $class;
}

sub delete_all
{
    my $self = shift;
    $self->parms()->clear();
}

# ...etc

1;
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A quick test of the above code appears to be ok...

Hope that helps