Fix possible wrong autocorrection in namespace on Style/PerlBackrefs

changelog/fix_possible_wrong_autocorrection_in_namespace_on.md

@@ -0,0 +1 @@
+* [#10975](https://github.com/rubocop/rubocop/pull/10975): Fix possible wrong autocorrection in namespace on `Style/PerlBackrefs`. ([@r7kamura][])

lib/rubocop/cop/style/perl_backrefs.rb

@@ -83,10 +83,31 @@ def preferred_expression_to(node)
           end
         end
 
+        # @private
+        # @param [RuboCop::AST::Node] node
+        # @return [String, nil]
+        def preferred_expression_to_node_with_constant_prefix(node)
+          expression = preferred_expression_to(node)
+          return unless expression
+
+          "#{constant_prefix(node)}#{expression}"
+        end
+
+        # @private
+        # @param [RuboCop::AST::Node] node
+        # @return [String]
+        def constant_prefix(node)
+          if node.each_ancestor(:class, :module).any?
+            '::'
+          else
+            ''
+          end
+        end
+
         # @private
         # @param [RuboCop::AST::Node] node
         def on_back_ref_or_gvar_or_nth_ref(node)
-          preferred_expression = preferred_expression_to(node)
+          preferred_expression = preferred_expression_to_node_with_constant_prefix(node)
           return unless preferred_expression
 
           add_offense(

spec/rubocop/cop/style/perl_backrefs_spec.rb

@@ -143,4 +143,25 @@
       /#{Regexp.last_match(1)}/
     RUBY
   end
+
+  it 'autocorrects $1 to ::Regexp.last_match(1) in namespace' do
+    expect_offense(<<~RUBY)
+      module Foo
+        class Regexp
+        end
+
+        puts $1
+             ^^ Prefer `::Regexp.last_match(1)` over `$1`.
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      module Foo
+        class Regexp
+        end
+
+        puts ::Regexp.last_match(1)
+      end
+    RUBY
+  end
 end