PATHEXT is an environment variable of MS Windows NT/2000/XP.

The function is to determine which file extensions mark files, that are executable from every commandline!

The default value is on my MS Windows 2000 system:

 .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;

I added to be able to execute tcl script files from every commandline:

 .TCL;.TK;.TCLSH;

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