I have a list of, possibly sparse, numbers. I wish to find a range of the numbers from the list between values. These bracketing values may not be in the list itself (the low end should use the next number and the high end should use the previous). I have a working algorythm, but am not sure if it's best. This sounds like it might be a standard problem, and consequently have a standard solution. 
my(@F, @G);
@F = (
      1,
      2,
      4,
      8,
      16,
      32..64
     );

#Generate a reverse map
for(my $i=0; $i<scalar @F; $i++){
  $G[$F[$i]] = $i;
}

sub range{
  my($lo, $hi) = @_;
  $lo++ until defined($G[$lo]);
  $hi-- until defined($G[$hi]);
  return $lo .. $hi;
}

print join(',', range(25,35)), "\n";
print join(',', range(50,75)), "\n";

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In reply to mapping lists by belg4mit

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