Added a test for Instant.perl.

Author: Kodi Arfer

S32-temporal/DateTime-Instant-Duration.t

@@ -1,6 +1,8 @@
 use v6;
 use Test;
 
+plan 33;
+
 =begin pod
 
 DateTime is the only means of constructing arbitrary Instants,
@@ -121,7 +123,9 @@ is DateTime.new(dtpi 2006,  1,  1,    0,  0,  0.2).second,  0.2, 'Round-tripping
     is ~$dt, '31/12/1999 59s4m18h', 'DateTime.new(Instant) with time zone and formatter';
 }
 
-
-done;
+{
+    my $i = dtpi 1988, 11, 22,   18, 42, 15.9;
+    is $i.perl.eval, $i, 'Round-tripping Instant.perl';
+}
 
 # vim: ft=perl6