This is one of the example sorts in Uri Guttman and Larry Rosler's paper on sorting in Perl.

They use the following:

@out = sort {
    pack('C4' => $a =~
      /(\d+)\.(\d+)\.(\d+)\.(\d+)/)

    cmp

    pack('C4' => $b =~
      /(\d+)\.(\d+)\.(\d+)\.(\d+)/)
  } @in;
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