diff --git a/flax/add_sub b/flax/add_sub
new file mode 100644
--- /dev/null
+++ b/flax/add_sub
@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+# usage: add_sub [-l sublevel] subname subterms_to_add_to
+
+from optparse import OptionParser
+
+parser = OptionParser()
+parser.add_option('-l', '--level', default='0')
+opts, args = parser.parse_args()
+print 'debug', opts, args
+
+sub = args.pop(0)
+print "adding '%s' at %s" % (sub, opts.level)
+
+for subterm in args:
+    print "subterm", subterm
+    print
+    filename = 'subterms/%s' % subterm
+    subs = [line.split(None, 1)[0] for line in file(filename).readlines()]
+    if sub not in subs:
+        f = file(filename, 'a')
+        print 'appended!'
+        print >>f, "%s %s" % (sub, opts.level)