allow perlbrew lib create to fail
allow perlbrew lib create to fail

the perlbrew library may already exist. probably should be `command || true` but it wouldn't work without the `set +e; command; set -e;` for me

berkmancenter/mediacloud,berkmancenter/mediacloud,berkmancenter/mediacloud,berkmancenter/mediacloud,berkmancenter/mediacloud