I think this is in Knuth, but I'm too lazy to look it up. Assuming that $N and $M are set: 
my @a = map {my $e = rand $N -- < $M; $e && $M --; $e || 0} 1 .. $N;

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Abigail

In reply to Re: random elements with fixed totals by Abigail-II
in thread random elements with fixed totals by ysth

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