Custom extension error

[nifl]

Following the docs, I set up the curl example
{ "head" : "curl -I -s -L {{args}}" }

Running glue head www.supafresh.com, returns

Traceback (most recent call last):
  File "Glue in /Users/nifl/Library/Application Support/Sublime Text 3/Installed Packages/Glue.sublime-package", line 163, in muterun_runner
  File "Glue in /Users/nifl/Library/Application Support/Sublime Text 3/Installed Packages/Glue.sublime-package", line 382, in muterun
  File "./json/__init__.py", line 319, in loads
  File "./json/decoder.py", line 352, in decode
  File "./json/decoder.py", line 368, in raw_decode
  File "./json/scanner.py", line 38, in _scan_once
  File "./json/decoder.py", line 176, in JSONObject
ValueError: Expecting property name enclosed in double quotes: line 2 column 9 (char 10)