Something like:

$out .= LJ::ehtml(join ', ', sort { $a cmp $b } map { $_->{name} } (values %$tags)[0..9]);

if you want the first 10 without sorting, or:

$out .= LJ::ehtml(join ', ', (sort { $a cmp $b } map { $_->{name} } values %$tags)[0..9]);

if you want the first 10 sorted by the name field.

(Also, added the missing comparison function to your sort, assuming you want string ordering. Adjust as needed.)