my @final_result;
iterate(@entries);

sub iterate {
    my ( $top_entry, @entries ) = @_;
    my @keepers;

    for (@entries) {
        my $comparison = compare_sub( $top_entry, $_ );
        if ( $comparison > $user_defined_value ) {
            push @keepers, $_;
        }
    }

    if (...) {
        iterate(@keepers);
    }
    else {
        @final_result = ...;
    }
}