The "correct" solution is to iterate through the indexes, not the elements themselves:

for ($i = 0; $i < @array; $i++) {
   if (matches($array[$i])) {
      $found = $array[$i-1];
   }
}
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If you want to insist doing it in foreach style:

foreach $item (@array) {
   if (matches($item)) {
      $found = $last;
   }
   $last = $item;
}
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Originally posted as a Categorized Answer.