If you change: 

$lights{$light} ? $lights{$light} = 0 : $lights{$light} = 1;

[download]
to: 
$lights{$light} = $lights{$light} ? 0 : 1;

[download]
it works ok.

From perlop:

If the argument before the ? is true, the argument before the : is returned, otherwise the argument after the : is returned.

update:

Added quote from the docs

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

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