(?:(?{local $q [2] = $nodes [0]})|
   (?{local $q [2] = $nodes [1]})|
   (?{local $q [2] = $nodes [2]})|
   (?{local $q [2] = $nodes [3]})|
   (?{local $q [2] = $nodes [4]})|
   (?{local $q [2] = $nodes [5]})|
   (?{local $q [2] = $nodes [6]})|
   (?{local $q [2] = $nodes [7]}))
(?(?{$q [2] eq $q [0] ||
     $q [2] eq $q [1] ||
     !$graph {$q [1]} {$q [2]}})x|)