Hmm...

system qq[ start /b /wait /low perl C:/Perl_activate/Run_this.pl $var 
+]
  or print STDERR "couldn't exec the perl program: $!";
[download]

Is system on Windows so much different that it returns a non-zero value on success (i.e. do Windows commands successfully exit with a non-zero status)?

Otherwise, that should be

system qq[ start /b /wait /low perl C:/Perl_activate/Run_this.pl $var 
+]
  and print STDERR "couldn't exec the perl program: $!";
[download]

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}