Call a function in a shared library

use NativeCall;

constant libX11 = '/usr/lib/x86_64-linux-gnu/libX11.so.6';

sub XOpenDisplay(Str $s --> int32) is native(libX11) {*}
sub XCloseDisplay(int32 $i --> int32) is native(libX11) {*}

if try my $d = XOpenDisplay ":0.0" {
    say "ID = $d";
    XCloseDisplay($d);
}
else {
    say "No library {libX11}!";
    say "Use this window instead --> ⬜";
}

Output:

ID = 124842864