[perl #76998] [BUG] capture variable does not parse for building a pair of the form :$

[Christian Bartolomaeus via RT]

This now has a test in S05-capture/match-object.t (cmp. 
https://github.com/perl6/roast/commit/15cd5a89f8fcfac7d0a3ae13afbc2c790316c8ef)

All credits to timotimo, who explained both test and procedure to close this 
ticket: http://perl6advent.wordpress.com/2013/12/17/day-17-of-a-new-contributor/