yitz_ 1235627615 learn # read v <<< "y0"; n=${v#y}; r=y$((n+1)); echo $r
yitz_ 1235627625 forget
yitz_ 1235627629 learn # read v <<< "yy"; n=${v#y}; r=y$((n+1)); echo $r
yitz_ 1235627641 forget
yitz_ 1235627645 learn # read v <<< "y1"; n=${v#y}; r=y$((n+1)); echo $r