Macro run_shell 

macro_rules! run_shell {
    (@cmd ($cmd:expr) -b, $($tail:tt)*) => { ... };
    (@cmd ($cmd:expr) -C, $($tail:tt)*) => { ... };
    (@cmd ($cmd:expr) -d $delay:expr, $($tail:tt)*) => { ... };
    (@cmd ($cmd:expr) -t $target_pane:expr, $($tail:tt)*) => { ... };
    (@cmd ($cmd:expr) $shell_command:expr, $($tail:tt)*) => { ... };
    (@cmd ($cmd:expr) $command:expr, $($tail:tt)*) => { ... };
    (@cmd ($cmd:expr)) => { ... };
    () => { ... };
    (($cmd:expr), $($tail:tt)*) => { ... };
    ($($tail:tt)*) => { ... };
}

Manual

tmux ^3.2:

run-shell [-bC] [-d delay] [-t target-pane] [shell-command]
(alias: run)

tmux ^1.8:

run-shell [-b] [-t target-pane] shell-command
(alias: run)

tmux ^1.2:

run-shell shell-command
(alias: run)

tmux ^1.1:

run-shell command
(alias: run)