Change /{{/ in regex to /\{\{/

Perl v5.22 is deprecating unescaped left braces in a regular expression
pattern.  This module has been broken since this was put into effect in
v5.21.2:
http://www.cpantesters.org/cpan/report/a9a07ed6-7c7b-11e4-ad19-d06752b25338

This was just brought to my attention by
https://rt.perl.org/Ticket/Display.html?id=122146#txn-1321681

Even though no warning messages were being displayed, the test was
failing.  I looked for left braces through the code and found these two.
When I add the backslashes, the tests start passing again.  There should
be no harm in escaping any punctuation character in a pattern in any
Perl 5 release, so this should work in any version.