Macro last_pane 

macro_rules! last_pane {
    (@cmd ($cmd:expr) -d, $($tail:tt)*) => { ... };
    (@cmd ($cmd:expr) -e, $($tail:tt)*) => { ... };
    (@cmd ($cmd:expr) -Z, $($tail:tt)*) => { ... };
    (@cmd ($cmd:expr) -t $target_window:expr, $($tail:tt)*) => { ... };
    (@cmd ($cmd:expr)) => { ... };
    () => { ... };
    (($cmd:expr), $($tail:tt)*) => { ... };
    ($($tail:tt)*) => { ... };
}

Select the last (previously selected) pane

Manual

tmux ^3.1:

last-pane [-deZ] [-t target-window]
(alias: lastp)

tmux ^2.0:

last-pane [-de] [-t target-window]
(alias: lastp)

tmux ^1.4:

last-pane [-t target-window]
(alias: lastp)