A easy example to tell you what is "2>&1" in Perl

You can decide if make the output shown on command screen by using 2>&1 or NUL

Testing script:

print "without null \n";

system("dir 2>&1");

print "with null \n";

system("dir > NUL");

print "end \n";

Result:

C:\Rebecca\script\perl\Unicode>perl calculate.pl

without null

Volume in drive C isOSDisk

Volume Serial Numberis BA23-5612

Directory of C:\Rebecca\script\perl\Unicode

01/22/2015  04:59PM    <DIR>          .

01/22/2015  04:59PM    <DIR>          ..

01/22/2015  04:58PM               227 calculate.pl

01/22/2015  09:19AM               194 unicode_test_v1.pl

01/21/2015  05:23PM               193unicode_test_v1.pl.ba

3File(s)            614 bytes

2Dir(s)  175,476,535,296 bytes free

with null   #you can see with NUL, there isn‘t any output shown here

end