I think I may have figured it out

renderers/markdown.moon

@@ -19,7 +19,18 @@ convert = =>
   (md_source) ->
     filename = os.tmpname!
     write_exec md_source, @cmd, filename
-    Path.read_file filename
+    a = Path.read_file filename
+    require("moon").p a
+    a
+
+    -- fname = os.tmpname!
+    -- with io.open fname, "w"
+    --   \write md_source
+    --   \close!
+    --
+    -- p = io.popen (@cmd)\format lang, fname
+    -- out = p\read"*a"
+    -- out
 
 -- config command like this in site.moon:
 -- require("renderers.markdown").cmd = "pandoc --mathjax >"
@@ -28,7 +39,11 @@ class PandocRenderer extends require "sitegen.renderers.markdown"
   escape_cosmo = @escape_cosmo
   pandoc = convert @
 
-  cmd: "pandoc >"
+  -- cmd: "pandoc >"
+  cmd: "pandoc --mathjax --lua-filter pygments.lua >"
+  -- cmd: "pygmentize -f html -l %s %s"
+  -- cmd: "pygmentize -f html -l %s %s -x"
+  -- cmd: "pygmentize -f html -l moonscript.py test.moon -x -o lexer-test.html"
 
   render: (page, md_source) =>
     md_source = page\pipe "renderer.markdown.pre_render", md_source