1) Right click on 'My Computer' and select properties. 2) Move along to the Advanced tab. 3) Click on Environment Variables. 4) In the System Variables double click on PATHEXT. 5) Append a ';.pl' to the end or a '.pl;' to the beggining of the Variable value box. 6) Click on all of the OK's and Apply's, restart your CLI and try it out.