I am trying to create a regular expression for what think should be pretty simple straight forward syntax but I am not having any luck

I want to support parsing an ini setting defined like:
RepeatingGroup = <name> [, Flatten][, in|out]]

I want "Flatten" and "in|out" to be able to be used in either order.

Examples:

RepeatingGroup = Waiver, Flatten, out
RepeatingGroup = Waiver, out
RepeatingGroup = Waiver, out, Flatten
RepeatingGroup = Waiver , in
RepeatingGroup = Waiver , Flatten

This is the expression I am trying to use

"RepeatingGroup\s*=\s*(?<GroupID>\b[^ \t]+\b)\s*(?=\s*,\s*(?<Flatten>\
+bFlatten\b))?(?=\s*,\s*(?<Direction>\b(in|out)\b))?$"

[download]

Many examples I find online suggest the use of the ?= lookahead.

What am I doing wrong?

2017-08-05 Athanasius added code tags

In reply to Regex with lookahead by ericwsf

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