The two-step seems the best (and only?) option here ...
As an exercise, I added basic macro argument-handling to Damian's demo_cpp.pl, included in Parse-RecDescent.
In demo_cpp.pl, change the "demacro" function to:

sub demacro($)
{
    my $text = shift;
    while (($macro,$pkg) = each %macro )
    {
        my $defn = $$pkg[0];
        if (defined $$pkg[1]) {
            my @args = @{$$pkg[1]};
            while ($text =~ m/($macro\((.*?)\))/g) {
                my $oA = length($`), $oZ = length($&);
                my @vals = split /\s*,\s*/, $2;
                (@args eq @vals)
                    or die "Bad arg count for macro '$macro'\n";
                my $_defn = $defn;
                for ($i=0; $i<@args; $i++) {
                    $_defn =~ s/$args[$i]/($vals[$i])/g;
                }
                substr($text, $oA, $oZ) = $_defn;
            }
        }
        else {
            $text =~ s/$macro/$defn/;
        }
    }
    return $text;
}
[download]

And change the "macrodef" rule to:

    macrodef : '#define' /[a-z]\w*/i
        '(' <leftop: /[a-z]+/i ',' /[a-z]+/i> ')'  /.*/
            { $::macro{$item[2]} = [ $item[-1], $item[4] ]; }
         | '#define' /[a-z]\w*/i  /.*/
            { $::macro{$item[2]} = [ $item[-1] ]; }
[download]

This would process #define's like in:

#define        add(a,b,c)        (a+b+c)
#define        mult(d,e)        (d*e)
#define        pi            (3.1415)
main( ) {
    add(1,2,3);
    mult(4,5);
    float p = pi;
}
[download]

Note that this is no less "naive" than the original demo -- simple string substitution is used for argument instantiation (though this does add parens around each arg instance to preserve operator precedence). E.g., using args "a" and "ab" would fail since the "a"-instantiation would intrude on part of the "ab". A real algorithm would need to rectify this (with smart tokenization, etc.).

Thanks for the help.
Jim