sub nextpart {
    ## collect all the trailing 1s
    my $x = 0;
    $x += pop while @_ and $_[-1] == 1;
    return if ! @_;

    ## collect 1 from the rightmost remaining guy
    $_[-1]--; $x++;

    ## re-distribute the collected amount in increments of $_[-1]
    while ($x > $_[-1]) {
       push @_, $_[-1];
       $x -= $_[-1];
    }
    push @_, $x;

    @_;
}

## example usage:

my @part = (5);
do {
    print "@part\n";
} while (@part = nextpart @part);

__OUTPUT__
5
4 1
3 2
3 1 1
2 2 1
2 1 1 1
1 1 1 1 1