Concur

# concur, channels, duration literals (design/concurrency.md, 2026-09-22).
fn fetch [lent 'url': str.utf8] -> str.utf8 { return "page of " ++ 'url'; }

MAIN {
    # Each task sends on its own channel, so the pages print in the same order whichever finishes first.
    let 'from_a' := channel[str.utf8];
    let 'from_b' := channel[str.utf8];
    let 'a' := "a.com";
    concur with [lend 'from_a', give 'a'] { channel.send[lend 'from_a', value fetch[lend 'a']]; }
    concur with [lend 'from_b'] { channel.send[lend 'from_b', value fetch["b.com"]]; }
    let 'page_a' := channel.take[lend 'from_a'] otherwise str.empty;
    let 'page_b' := channel.take[lend 'from_b'] otherwise str.empty;
    std::print.useful['page_a', newln, 'page_b', newln];
    let 'd' := 5 seconds;
    std::print.useful['d', " ", 1500 millis, " ", 1 hour, " ", 5 seconds equal_to 5_000 millis, newln];
}