confused about 'try'

Been playing with perl6 and it is truly amazing.

I'm somewhat confused as to when I should should wrap subroutine
invocations with `try`. My `CATCH` clauses seem to be able to catch thrown
Exception instances if I use `try` or not. I see in the "Exceptional Perl
6" slide deck (
http://moritz.faui2k3.org/files/talks/2013-yapc-p6-exceptions/ ), there
seems to be an indication that `try` should be used when I want to access a
Backtrace...is there something here I am missing?

Thanks
Brad