=head2 start_xserver($parallel)
Starts C<$parallel> (or number of cores * 2 if undef) Xephyr processes (see
-http://www.freedesktop.org/wiki/Software/Xephyr/) and returns two arrayrefs: a
+https://www.freedesktop.org/wiki/Software/Xephyr/) and returns two arrayrefs: a
list of X11 display numbers to the Xephyr processes and a list of PIDs of the
processes.
# First get the last used display number, then increment it by one.
# Effectively falls back to 1 if no X server is running.
- my ($displaynum) = map { /(\d+)$/ } reverse sort glob($x_socketpath . '*');
+ my ($displaynum) = reverse sort { $a <=> $b } map{ /(\d+)$/ } glob($x_socketpath . '*');
$displaynum++;
say "Starting $parallel Xephyr instances, starting at :$displaynum...";