my $code = qq(
      [head]
      Head text...
      [body]
      Body text...
      [something else]
      more text..
   );                     #example of text

   $code =~ s/\n//g;      #remove all the newlines
   $code .= "\n";         #add one to the end

   $formatCode($code);

   sub formatCode{
      my $str = $_[0];

      $str =~ s#\[(.*?)\](.*?)(\[.*?\]|\n)#<div class="$1">$2</div>#ig;
      print $str;
   }

##</code><code>##

$str =~ s#\[(.*?)\](.*?)(?=\[.*?\]|\n)#<div class="$1">$2</div>#ig;