Just set $prev lower down and initialise outside of loop. 
$prev = <some dummy value>;
for (......) {
    $data = <get data>;
    $element = <get element>;
...
    process data allowing for dummy value in $prev
...
    $prev = $element;
}

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In reply to Re: Remember previous element in a loop by tweetiepooh
in thread Remember previous element in a loop by Anonymous Monk

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