lookahead ?

Ok, now the line I'm trying to deal with is "some amount of whitespace,
then some text, then starting at column 48 a number, followed by a period,
followed by another number".  I want to capture the text (the "title"),
and the two numbers (major and minor versions):

line: title // <reject: $thiscolumn != 48> major \. minor

title: ??WHAT GOES HERE??
major: digits
minor: digits

digits: /\d+/

In a regex(p)?, I think I'd know what to do: positive lookahead on the
whitespace:

my ($title, $major, $minor) =
    $line =~ m/^\s*        # leading whitespace
	      (.*?)        # the title
              (?:\s+(?=\d+\.\d+\s*$)) # the space preceeding the numbers
              (\d+)        # the major version number
              \.
              (\d+)        # the minor version number
	      /x;

Can I accomplish this in a RD grammer without changing <skip:> ?

Thanks (yet again),

-Aaron