s{((?:(?:<span>)?.(?:</span>)?){80})}{$1\n}g 

##</code><code>##

 
#!perl 
$_ = "<span>1</span>";
s{((?:(?:<span>)?.(?:</span>)?){10})}{$1\n}g;
print "$_\n";
__END__
<span>1</s
pan>