$ perl -wE 'given (1) {2}'
given is experimental at -e line 1.
Useless use of a constant (2) in void context at -e line 1.
$ perl -wE 'given (1) {2}' 2> /tmp/err
$ cat /tmp/err
given is experimental at -e line 1.
Useless use of a constant (2) in void context at -e line 1.
$