the first part build a hash of arrays with the numbers as the key.

%h = ( 
         '1' => [
                   'hello',
                   'you',
                   'tree'
                 ],
          '3' => [
                   'sun',
                   'grass'
                 ],
          '2' => [
                   'people',
                   'fun'
                 ],
         ...
);
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The second for loop grap the array and join the words. To grap a entry use

  $num = 1;
  $string = join '', @{$h{$num}}; # string is now helloyoutree
  $num = 4; # select the string with number 4 ( lovefood )
  $string = join '', @{$h{$num}};
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