Argument "" isn't numeric in numeric ge (>=) at C:/Perl/site/lib/Tk/Chart.pm line 1112.
[WARNING] : -yminvalue and -ymaxvalue do not include all data
 at C:/Perl/site/lib/Tk/Chart/Lines.pm line 904
[BE CARREFUL] : -ymaxvalue option must be a number or real number
 at C:/Perl/site/lib/Tk/Chart/Lines.pm line 905

Process completed with exit code 255