My guess (I don't use Windows, but 'system "clear"' works on my Linux/bash/xterm, but `clear` doesn't, so I expect the reason is the same) is that 'cls' on Windows, just like 'clear' on Linux/Unix print out an escape sequence to standard out, which gets interpreted by the terminal driver to clear the screen.

The use of `` or qx makes that Perl gets the output of the command, not the terminal driver. 

$ perl -wle '$_ = `clear`; s/(.)/sprintf "0x%02x", ord $1/ge; print'
0x1b0x5b0x480x1b0x5b0x4a
$ perl -we 'print chr for 0x1b,0x5b,0x48,0x1b,0x5b,0x4a'
$ # Clears the screen!
$ clear | cat -v  
^[[H^[[J

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Abigail

In reply to Re: The difference between [system] and `backticks` and [qx//] (on win32) by Abigail-II
in thread The difference between [system] and `backticks` and [qx//] (on win32) by BrowserUk

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