$tiu => $min && $tiu < $max
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My guess is, this statement (on the lines mentioned in the warnings) should be
    $tiu>= $min && $tiu < $max

Note that  => is the 'fat comma', not the  >= 'greater than or equal to' comparator.

Updates:

1. BTW: Please use  <readmore> tags when posting a large chunk of code such as that in the OP. Please see Markup in the Monastery.
2. The statement
       $tiu => $min && $tiu < $max
   in scalar context (as imposed by the  if conditional) is the same as
       ($tiu, $min && $tiu < $max)
   in which the  $tiu scalar is evaluated and its value is thrown away (i.e., 'used uselessly'), and then the clause  $min && $tiu < $max is evaluated and becomes the final value of the statement. I doubt the latter clause is what you intended.