Document exploding sunk Proc trap

There were a few RTs involving.

doc/Language/traps.pod6

@@ -404,6 +404,25 @@ The nice thing about the distinction here is that it gives the developer the
 option of passing pairs as either named or positional arguments, which can be
 handy in various instances.
 
+=head1 Exception Handling
+
+=head2 Sunk C<Proc>
+
+Some methods return a L<Proc> object. If it represents a failed process, C<Proc> itself
+won't be exception-like, but B<sinking it> will cause an L<X::Proc::Unsuccessful>
+exception to be thrown. That means this construct will throw, despite the C<try> in place:
+
+    try run("perl6", "-e", "exit 42");
+    say "still alive";
+    # OUTPUT: The spawned process exited unsuccessfully (exit code: 42)
+
+This is because C<try> receives a C<Proc> and returns it, at which point it sinks and
+throws. Explicitly sinking it inside the C<try> avoids the issue:
+
+    try sink run("perl6", "-e", "exit 42");
+    say "still alive";
+    # OUTPUT: still alive
+
 =end pod
 
 # vim: expandtab shiftwidth=4 ft=perl6