my @data;
foreach ( 1 .. 100 ) {
    push @data, [ map { rand(200) - 100 } 1 .. 100 ];
}

my $pivot = 0;
my @sorted = keysort {
    my $v = $_;
    my @v = keysort { $_ > $pivot ? 1 : -1 } @{$v};
    $v[50]
} @data;