Add a test for defining a circumfix operator from a single constant.

S06-operator-overloading/sub.t

@@ -2,7 +2,7 @@ use v6;
 
 use Test;
 
-plan 84;
+plan 86;
 
 =begin pod
 
@@ -502,4 +502,11 @@ Testing operator overloading subroutines
     is 5 ° 5, "55", 'can define and use operator with a sigiled constant as symbol';
 }
 
+{
+    lives-ok { constant $x = "µ, @"; sub circumfix:<<$x>>($) { 42 } },
+        'can define circumfix using << >> and both delimiters from the same constant';
+    my $test = EVAL 'constant $x = "µ, @"; sub circumfix:<<$x>>($) { 42 }; µ 5 @';
+    is $test, 42, 'can define and use circumfix using << >> and both delimiters from the same constant'
+}
+
 # vim: ft=perl6