PRX modifier "i" and "?"

Not all perl regular expressions are supported by PRX functions.

However, it does support two useful modifers: "i" and "?"
case-insensitive modifer "i":
'/substring/i'

parens non-capturing modifer "?":
'/(?:substring1)/'

And they can be used together:
'/(?i:substring)/'
'/(?-i:substring)/'
'/(?-i:substring1)substring2/i'