#!/usr/bin/perl
use strict;
use warnings;
use Want;

my %obj;
sub cool :lvalue {
    my $key = shift;
    my %ok = map { $_ => 1 } 1..7;
    my $junk;

    if ( want( 'LVALUE ASSIGN' ) ) {
        if ( ! $ok{ $key } ) {
            warn "$key is not valid";
            lnoreturn;
        }
        else {
            my ($rval) = want( 'ASSIGN' );
            if ( ! $ok{ $rval } ) {
                warn "$rval as rval is not valid";
                lnoreturn;
            }
            $obj{ $key } = $rval;
        }
        lnoreturn;
    }
    elsif ( want( 'RVALUE' ) ) {
        if ( ! $ok{ $key } ) {
            warn "$key is not valid";
            rreturn $junk;
        }
        else {
            rreturn $obj{ $key };
        }
    }
    else {
      warn "Houston, we have a problem";
    }
    return;
}
cool( 1 ) = 3;
print cool( 1 ), "\n";
cool( 5 ) = 42;
cool( 9 ) = 3;
print "$_ : $obj{$_}\n" for keys %obj;
__END__
3
42 as rval is not valid at foo.pl line 20.
9 is not valid at foo.pl line 14.
1 : 3