pwd: /out/package
ppid: 2698
   1: WRITELN echo abc > 1.txt > 2.txt
   2: WRITELN echo abc > 1.txt >> 2.txt
   3: WRITELN echo abc > 1.txt | grep abc
   4: WRITELN exit
exit: 0

mumsh $ error: duplicated output redirection
mumsh $ error: duplicated output redirection
mumsh $ error: duplicated output redirection
mumsh $ exit

mumsh $ error: duplicated output redirection
mumsh $ error: duplicated output redirection
mumsh $ error: duplicated output redirection
mumsh $ exit