sub map2(&@){ 
    my $code = shift; 
    map $code->( shift, shift ), 0 .. $#_/2 
}

sub grep2(&@){ 
    my $code = shift; 
    map{ 
        my @pair = (shift,shift); 
        $code->( @pair ) ? @pair : ()
    } 0 .. $#_/2 
}