Not much sense, they can see it in the diagnostics, and the warning
message is a bit confusing.
Use of uninitialized value $this in pattern match (m//) at x:\test.t line 6.
It reports the right location, but there's no $this from the user's
This came in because like used to supress all warnings. That was
fixed in 8b2f0c6 but it let
uninit warnings slip in.