diff --git a/filla.nu b/filla.nu
index 4a00237..753142a 100755
--- a/filla.nu
+++ b/filla.nu
@@ -78,3 +78,22 @@ def "main folnum_test" [...paths] {
     }
   )
 }
+
+def "main folnum" [...paths] {
+
+  ($paths |
+
+    each {|f|
+
+      let folder = $f | path dirname
+
+      let foldernum = $folder | path basename | str replace -r '^\D*(\d+)\D*$' '$1'
+
+      let name = $f | path basename
+
+      let newname = $foldernum + '-' + $name
+
+      mv ($folder | path join $name) ($folder | path join $newname)
+    }
+  )
+}