To solve this problem assign the first seed to play last seeded player in the first round and against a higher seed each subsequent round.

Then simply rely on the round-robin algorithm of rotating an array's values while keeping one static to ensure that everyone plays against each other:

use strict;
use warnings;

my $num_players = 6;

my @players = (1..$num_players);
push @players, 'bye' if @players % 2; # Even number

my $num_rounds = @players - 1;

for my $round (1..$num_rounds) {
    # Fold array to assign matches
    my @matches = map {join('-', sort @players[$_, $#players - $_])} (
+0..@players/2-1);

    # Print Results
    print "$round) " . join(', ', @matches), "\n";
    
    # Rotate last position to second
    splice @players, 1, 0, pop(@players);
}
[download]

Results:

1) 1-6, 2-5, 3-4
2) 1-5, 4-6, 2-3
3) 1-4, 3-5, 2-6
4) 1-3, 2-4, 5-6
5) 1-2, 3-6, 4-5
[download]

This works with any number of players and rounds.

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