$ perl -le'qx{date abc}; print $?'
date: invalid date `abc'
256

##</code><code>##

$ perl -le'qx{cat some file}; print $?'
cat: some: No such file or directory
cat: file: No such file or directory
256

$ perl -le'qx{cat "some file"}; print $?'
0

##</code><code>##

$ perl -le'qx{echo foo | grep bar}; print $?'
256

$ perl -le'qx{echo foo | grep foo}; print $?'
0