#!perl -l chop while$_.=pop,print,s/.(?=(.))/chop($_=$&+$1)+$_/eg
#!perl -l $_=pop;print,s/.(?=(.))/chop($_=$&+$1)+$_/eg,chop while/./
#!perl -l $_=pop;print,s/(.)(?=(.))/chop($a=$1+$2)+$a/eg,chop while/./