stmuk added a test for this recently:
https://github.com/perl6/roast/commit/b4fc0fe9f11bb34e4442da7e1f945e8740d07c7c
I moved the test from S02-names-var/76608.t to
S02-literals/misc-interpolation.t (which is in 't/spectest.data').
The test passes on all rakudo backends.
# New Ticket Created by "Carl Mäsak"
# Please include the string: [perl #76608]
# in the subject line of all future correspondence about this issue.
# http://rt.perl.org/rt3/Ticket/Display.html?id=76608 >
rakudo: "foo$(my $x = 42)bar"; say $x
rakudo 3370f0: OUTPUT«===SORRY!===Redeclaration
