use constant BOOL => 0; 
our $BOOL = 0; 
cmpthese -1,{ 
    const => q[ 
        for(1..1e6){ 
            if(BOOL){ 
                my $n = 1; 
                $n *=$_ for 1 .. 1000;
            } 
        } 
    ], 
    var => q[ 
        for(1..1e6){ 
            if($BOOL){ 
                my $n = 1; 
                $n *=$_ for 1 .. 1000;
            } 
        } 
    ] 
};;
        Rate   var const
var   15.1/s    --  -22%
const 19.4/s   29%    --