my $len= 0;
   $text =~ s{(\s+)|([^\s<&]+)|(<[^<>]*>)|(&#?\w{1,10};)|(.)}{
      if(  $1  ) {
         $len= 0;
         $1;
      } elsif(  length( $2 )  ) {
         # $2 is the only case that can be "0" (ie. false)
         my $res= $2;
         my $tot= $len + length($res);
         if(  18 < $tot  ) {
            substr( $res, 18-$tot, 0 )= " ";
            $res =~ s/(\S{18})(?=\S)/$1 /g;
            # replace previous with following for [tye]s improvment
            # $res =~ s/(\S{9,18}\b|\S{18})(?=\S)/$1 /g;
            $res =~ /(\S*)$/;
            $len= length( $1 );
         } else {
            $len= $tot;
         }
         $res;
      } elsif(  $3  ) {
         $3;
      } else {
         my $res= $4 || $5;
         my $add= $5 ? 1 : int( length($4)/3 );
         $len += $add;
         if(  18 < $len  ) {
            $len= $add;
            " $res";
         } else {
            $res;
         }
      }
   }egis;

   return $text;