#!perl -l /.{$i}(.)/,$;=$ARGV[$i++%2],$_.=$;x($1||$;)until/.{$ARGV[2]}/;print$&
#!perl -l @_=@ARGV;/.{$i}(.)/,$;=$_[$i++%2],$_.=$;x($1||$;)until/.{$_[2]}/;print$&