Perhaps its to late, but i want to post my try, i did it before looking at others code:

for(1..$a){printf"%${\length($a*$a/2)}d",$-++;$_==++$?||redo;print$/;$
+?=0}
[download]

$anarion=\$anarion;

s==q^QBY_^=,$_^=$[x7,print