It looks to me like what you're trying to do is filter down the list to only those values which are "available". The way to filter down a list is, canonically, with grep.

  for my $nnot (
    map { $solution[-1] + $_, $solution[-1] - $_ }
    grep { $availableIntervals[$_] > 0 }
    (1 .. 11)
  ) {
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You can combine the map and the grep into a single map (similar to what suaveant alluded to, above):

  for my $nnot (
    map { 
      $availableIntervals[$_] > 0 
        ? ( $solution[-1] + $_, $solution[-1] - $_ )
        : ()
    } (1 .. 11)
  ) {
[download]

jdporter
The 6th Rule of Perl Club is -- There is no Rule #6.