Don't modify a variable that you're using elsewhere in an expression. At best, it's unclear. At worse, the result is undefined. 

$toggle = - --$toggle;

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should be 
$toggle = -( $toggle - 1 );

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which can be shortened to previously mentioned 
$toggle = 1 - $toggle;

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In reply to Re^3: Boolean counter? by ikegami
in thread Boolean counter? by DreamT

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