Is there something wrong with the (obvious?) just surround both groups with another outer set of parens (which then shifts the numerics down by one)? Should work with a named mark as well.

my $re = qr/(?<whole_enchilada> (?<Letter>\w+) (?<Digit>\s*\d+\s*)* )/
+x;
[download]

Edit: NVM, misread what was being asked. You could wrap the second set of parens outside the quantifier I believe but that's not going to preserve the separate matches. ENOCAFFEINE . . .

Edit 2: Playing with %- and friends I'm not finding anything obvious. The other suggestion about using minor ebil like embedded code pushing to an array sounds like the most promising.