record Point(int x, int y) { }
record square(Point upperLeft, Point lowerRight) { }

public class PatternVariables {
    void method(Object obj) {
        if (obj instanceof square(Point(int _, int y), _)) {  // violation
            System.out.println(y);
        }
    }
}
PS D:\CS\test> cat config.xml                                                                                
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
          "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
          "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">

<module name="Checker">
    <property name="charset" value="UTF-8"/>
 <module name="TreeWalker">
    <module name="PatternVariableName">
    </module>
 </module>
</module>
PS D:\CS\test> java  -jar checkstyle-10.14.2-all.jar -c config.xml  src/PatternVariables.java                
Starting audit...
[ERROR] D:\CS\test\src\PatternVariables.java:6:45: Name '_' must match pattern '^[a-z][a-zA-Z0-9]*$'. [PatternVariableName]
Audit done.
Checkstyle ends with 1 errors.