basically, replace arrTest with {$messages}, so:

@{$messages}       for @arrTest       (the whole array).
${$messages}[$i]   for $arrTest[$i]   (an element).
@{$messages}{0, 2} for @arrTest{0, 2} (a slice).
$#{$messages}      for $#arrTest      (the last index).
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The curly brackets are optional, btw.