Slightly updated probing logic based on Jason's code.

Signed-off-by: Jesse Vincent <jesse@keyboard.io>

bin/find-device-port-macos

@@ -55,15 +55,24 @@ sub try_for_raw_serialnum {
     # High Sierra sometimes has a mismatch between the serial number and the device
     # filename. I'm not sure why, but system_profiler has a serial number ending in "E",
     # whereas the device filename ends in "1". In fact, when I change HID.getShortName()
-    # to return "kbio02", the final character is replaced with a "1", so we should do the
-    # same here. If the serial number doesn't end in a digit, however, we may want to append
-    # rather than replace the last character with a 1.
+    # to return "kbio02", the final character is replaced with a "1". 
+    
     if ($serial_port_name =~ /\d$/) {
-        $serial_port_name =~ s/.$/1/;
+    	chop $serial_port_name;
+    	exit_with_port_if_exists($serial_port_name . "1");
     } else {
-        $serial_port_name .= "1";
+	# If the serial port name doesn't end with a digit, try -appending- rather than replacing 
+	# the last character of the port name
+    	exit_with_port_if_exists($serial_port_name . "1");
+    
+	# and if that didn't work, try replacing the last character with a "1" anyway.
+    	# Jason Koh reports that he saw this behavior as required on Catalina in May 2020.
+    
+    	chop $serial_port_name;
+    	exit_with_port_if_exists($serial_port_name . "1");
     }
-    exit_with_port_if_exists($serial_port_name);
+
+
 }
 
 sub try_for_location_id {