How to describe function arguments in PEG grammar

I'm still fighting with ambiguous grammar of Qt's qmake.

Now I can't find a way to describe function arguments that can contain parenthesis (e.g. regex):

functionName(arg1, "arg2", ^(arg3)+$)

I've tried to describe function call like this:

FunctionCall = Identifier space* "(" space* FunctionArgumentList? space* ")" space* eol*

FunctionArgumentList = FunctionArgumentString ((space* "," space* FunctionArgumentString)* / (blank* FunctionArgumentString)*)
FunctionArgumentString = ReplaceFunctionCall / TestFunctionCall / EnquotedString / RegularFunctionArgumentString
RegularFunctionArgumentString = RegularFunctionArgumentStringChar+
RegularFunctionArgumentStringChar = !(")" / blank / "," / quote / doublequote) SourceCharacter
SourceCharacter <- [\u0000-\uFFFC]

How do I add support for embedded parenthesis WITHOUT quotes/double quotes in such grammar? How do I distinguish the parenthesis inside function arguments and function closing one?

Valid function call example:

contains(CMAKE_INSTALL_LIBS_DIR, ^(/usr)?/lib(64)?.*)

Solution

Well, i found a pretty hacky solution myself:
just look further for a next statement.
Here is a simplified grammar fragment using this way:

FunctionCall = Identifier _* "(" _* FunctionArgumentList? _* ")" _*
FunctionArgumentList = CommaSeparatedList / FunctionArgument
CommaSeparatedList = FunctionArgument (COMMA_WS FunctionArgument?)+

FunctionArgument = FunctionArgumentImpl FunctionArgumentImpl*
FunctionArgumentImpl = EnquotedString / FunctionArgumentString
FunctionArgumentString = FunctionArgumentStringChar+
FunctionArgumentStringChar = !(COMMA / QUOTE / DOUBLEQUOTE / EndOfFunction) SourceCharacter

EndOfFunction = ")" _* (
     eoi / eol
    / "=" / "+=" / "*=" / "-=" / "~="
    / "," / "." / "_"
    / "(" / ")"
    "{" / "}" / ":" / "|"
)

COMMA_WS = _ "," _
COMMA = ","
QUOTE = "'"
DOUBLEQUOTE = '"'
BACKSLASH = "\\"
_ = [ \t]

Hope this will be useful for somebody.