use List::Util qw(min);
sub foo {}
$x = time();
foreach my $thing ( qw( x foo min time ) ) {
    printf "$thing is code: %s\n",
        ( ref *{$main::{$thing}}{CODE} ) ? 'Yes' : 'No';
}
__END__
x is code: No
foo is code: Yes
min is code: Yes
time is code: No