The problem is actually caused by the error reporting: https://github.com/rakudo/rakudo/blob/08b951c8f33cfc702c308e64efcb44f3ec725117/src/core/Exception.pm6#L2969
The only heuristic I’ve been able to find so far that the value of $ns{$_} suddenly is no longer fully qualified if the namespace doesn’t exist. I guess we can build some heuristic check on that, but it feels fragile. Perhaps nine / ugexe / jnthn have a better idea about that. > On 13 Apr 2018, at 08:34, Martin Barth (via RT) > <perl6-bugs-follo...@perl.org> wrote: > > # New Ticket Created by Martin Barth > # Please include the string: [perl #133107] > # in the subject line of all future correspondence about this issue. > # <URL: https://rt.perl.org/Ticket/Display.html?id=133107 > > > > requireing a non installed module leads to strange error if the name > starts with the name of a core module. e.g: > > >> perl6 -e 'require IO::Socket::Async::SSL' > IO::Socket::Async::SSL is a builtin type, not an external module > in block <unit> at -e line 1