use List::Util qw(shuffle max);
use Sort::Key::Top qw(ntop);
my @data = shuffle (0..100);
my $mediam = ntop -1, ntop 1 + @data / 2, @data; # O(N)
# or
# $mediam = max ntop 1 + @data / 2, @data; # O(N)
# $mediam = (ntopsort 1 + @data / 2, @data)[-1]; # O(NlogN)!
print "mediam: $mediam\n";