One small optimization you may do is to keep a temporary variable instead of calling length() at each iteration of each loop: 
sub substrings {
  my $string = shift;
  my @result = ();
  my $strlen = length $string;
  foreach my $length (1..$strlen) {
    foreach my $offset (0..$strlen-$length) {
      push @result, substr($string,$offset,$length);
    }
  }
  return @result;
}

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In reply to Re: Finding all substrings by thelenm
in thread Finding all substrings by TheHobbit

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