For starters,

if ($toggle) {
    $toggle = 0;
} else {
    $toggle = 1;
}
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can be written as

$toggle = $toggle ? 0 : 1;
[download]

And if you wanted a bitwise toggle, you could do

$toggle ^= 1;
[download]

But you asked for boolean, so you want the even simpler:

$toggle = !$toggle;
[download]