Delete document or list item versions using PowerShell

If you want... you can easily delete (or prune) the versions of list items or documents in a SharePoint list / library using PowerShell

Example: Prune the versions of all items in a list to a maximum of 20

$w = get-spweb http://myweb;
$l = $w.Lists["My List"];
$items = $l.Items;
foreach($item in $i){
if($item.Versions.Count -gt 20){
$vtr = $item.Versions.Count;
while($vtr -gt 20){
$vtr--;$item.Versions[$vtr].Delete()
}}}