It's not a closure that you're using, because a closure "binds" to lexical variables that exist *when the closure is created*. As you said, $W doesn't exist then; it exists *later*.

So what you should probably do instead is just something like this:

    my $g = Games::Grid->new
        (..., width => sub { $_[0]/4}, height => sub { $_[0] }, ...);
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And then do:

    $self->{terminal}->{WIDTH}  = $config{width}->($W);
    $self->{terminal}->{HEIGHT} = $config{height}->($H);
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In other words, pass $W and $H as args rather than rely on them being set when the sub is executed. If it were a closure, this would work; but it's not, bceause you're relying on the lexicals existing when you *execute* the subref, not when you *define* it.

String eval might be another way of accomplishing your goal, but I think you'd be better off just passing args.