Override HLL::Compiler.eval for multi-line input

The way this works is pretty dodgy, but it's good enough for
my experiment.  How this works is that we catch any exceptions
from evaluating the code; if there's an exception, it's an
X::Syntax::Missing, and it occurs at the end of the input string,
that means that more input is required.  Instead of just throwing
the exception at the user, we signal HLL::Compiler that we need
more input via self.needs-more-input

src/Perl6/Compiler.nqp

@@ -323,4 +323,30 @@ class Perl6::Compiler is HLL::Compiler {
         $line;
     }
 
+    method eval($code, *@args, *%adverbs) {
+        my $super := nqp::findmethod(HLL::Compiler, 'eval');
+        my $output := '';
+        my $ex;
+        try {
+            $output := $super(self, $code, |@args, |%adverbs);
+
+            CATCH {
+                if nqp::what($_).HOW.name(nqp::what($_)) eq 'BOOTException' {
+                    my $inner := nqp::getpayload(nqp::decont($_));
+
+                    my $ex-type := nqp::what($inner).HOW.name(nqp::what($inner));
+                    if $ex-type eq 'X::Syntax::Missing' {
+                        if $inner.pos() == nqp::chars($code) {
+                            return self.needs-more-input();
+                        }
+                    }
+                }
+                $ex := $_;
+            }
+        }
+        if $ex {
+            nqp::rethrow($ex);
+        }
+        $output;
+    }
 }