On the same lines if last-index-of-array variable, $#x, is assigned -1, array becomes empty (mentioned in perldata) ...

  DB<1> @x = ( 1 , 2 )

  DB<2> x @x
0  1
1  2
  DB<3> $#x = -1

  DB<4> x @x
  empty array
  DB<5>
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