Based on your sample characters (lowercase for $1 and digits for $2), I'd use:
RewriteRule ^L1-([a-z]+)-([0-9]+)\\.html$ section.php?cat_name=$1&cat=$2 [L]
When you are in a position to specify the characters used in your links, use them in the mod_rewrite code, too. It may be a small security issue to you but it would make hacking much easier for someone trying to break into your website. Besides, the inappropriate use of the :kaioken: EVERYTHING :kaioken: atom is the first indication that the coder has no idea what he/she is doing (and generally results in looping code).