while IFS= read -rd '' entry; do
   entry="${entry#./}"         # strip ./
   if [[ -d $entry ]]; then
      rename  'y/A-Z/a-z/; s/ /_/g; s/_-_/-/g; s/sometext//g; s/_extras/-extras/g' "$entry"
   else
      rename  'y/A-Z/a-z/; s/.(?=.*.)/_/g; s/ /_/g;  s/_-_/-/g; s/sometext//g; s/_extras/-extras/g' "$entry"
   fi
done < <(find . -iname '*' -print0)