Here's a "variation of the above" code fragment from an ancient script. It produces a set of numbers which can be used as indices in an array slice.

  # @indices = randomsubset(scalar @array, $size_of_subset);

  sub randomsubset {
      my @indices = 0 .. $_[0] - 1;
      my @subset = ();
      push @subset, splice(@d, int rand @indices, 1) for 1 .. @_[1];
      @subset;
  }

  print join (" ", randomsubset(50,5)), "\n";
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(The overly specific name indicates sloppy thinking on my part, for which I plead guilty.)

IIRC, there's something equivalent in the Cookbook.