update

lib/Slic3r/Polygon.pm

@@ -0,0 +1,13 @@
+package Slic3r::Polygon;
+use strict;
+use warnings;
+
+# a polygon is a closed polyline.
+use parent 'Slic3r::Polyline';
+
+sub grow {
+    my $self = shift;
+    return $self->split_at_first_point->grow(@_);
+}
+
+1;