xclose just closes window instead of killing its owner, which would tear
down all this owner's windows along.

Uses different utilities with a different set of drawbacks, though:

 *  wmctrl(1) needs to be installed.

 *  [slop][1] can be optionally installed from source but can be unreliable
    when selecting some windows, e.g. urxvt.

 *  If slop is missing, xwininfo is used, which, unlike xkill(1), has no
    way of cancelling the user action (r-click selects a window just the
    same as l-click).  We work around it using timeout(1), which is
    rather inconvenient, though.

But all in all, we're still better off than with xkill(1).

  [1]: https://github.com/naelstrof/slop