print "`set tmp` returned:", `set tmp`, " and had an exit code of:$?",$/;
print "`set non-existant-env` returned:", `set non-existant-env`, " and had an exit code of:$?",$/;

##</code><code>##

`set tmp` returned:TMP=D:\TEMP
 and had an exit code of:0
Environment variable non-existant-env not defined
`set non-existant-env` returned: and had an exit code of:256