DB<83> $_="x"x30


  DB<84> 1 while s/^( *x+)xx/ $1\n$&/;print "$_\n $1\n $1"
              xx
             xxxx
            xxxxxx
           xxxxxxxx
          xxxxxxxxxx
         xxxxxxxxxxxx
        xxxxxxxxxxxxxx
       xxxxxxxxxxxxxxxx
      xxxxxxxxxxxxxxxxxx
     xxxxxxxxxxxxxxxxxxxx
    xxxxxxxxxxxxxxxxxxxxxx
   xxxxxxxxxxxxxxxxxxxxxxxx
  xxxxxxxxxxxxxxxxxxxxxxxxxx
 xxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
              xx
              xx