I like that better than expecting a ->param, since that breaks it away from the contract of purely hash->hash.

Adding a branch breaks no contracts

sub build_cgi_struct
{
    my ($iv, $errs, $conf) = @_;
    
    use Scalar::Util qw(blessed);
    my $blessed = blessed $iv;
    my $splitnull = 1;
    if( $blessed and UNIVERSAL::can( $iv, 'param') ){
        $splitnull = 0;
        if( $iv->isa('CGI') ){
            $iv = $iv->{"param"} ; # cheat :)
        } else {
            $iv =  { map { $_ => [ $iv->param($_) ] } $iv->param  };
        }
    }
    ...
    ... if $splitnull;
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