V:\>perl -MO=Deparse -e "$x = FOO + 7 + 9"
$x = 'FOO' + 7 + 9;
-e syntax OK

V:\>perl -MO=Deparse -e "use constant FOO => 8; $x = FOO + 7 + 9"
use constant ('FOO', 8);
$x = 24;
-e syntax OK