You don't seem to understand that a long is an INTEGER type, so can't hold a float.

use Inline C;

print type_def();

#non_existant_function();

__END__
__C__

void type_def () {
    long foo = 38.5;
    if ( foo == 38 ) 
        printf("Foo is truncated to integer %d\n", foo );
}
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Uncomment the non_existant_function and you will generate the .al error - it can't autoload the non existant function.