There are currently only two flags available for use in regular
expression filters in ansible, which appear to be 'ignorecase' and
'multiline':
https://github.com/ansible/ansible/blob/devel/lib/ansible/plugins/filter/core.py
You're not entirely bound by these restrictions, because it's possible
to set flags by having your expression start with them:
https://docs.python.org/2/library/re.html (at the 'iLmsux' header).
DIck