Run the code with -MO=Deparse,-p, and the line with the ternary operator becomes: 
   (($lights{$light} ? ($lights{$light} = 0) : $lights{$light}) = 1);

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You can see that the 2nd assignment operator has lower precedence than the ternary operator. So this says,
If $lights{$light} is true, then assign 1 to the result of "$lights{$light}=0", otherwise assign 1 to the result of $lights{$light}.
... which is not what you want. A better way to use the ternary here is: 
  $lights{$light} = $lights{$light} ? 0 : 1;

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Or even better still is probably: 
  $lights{$light} = ! $lights{$light};

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which toggles $lights{$light} between true & false.

blokhead

In reply to Re: Ternary if versus normal if question by blokhead
in thread Ternary if versus normal if question by tphyahoo

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