A more efficient way to achieve what you want, is just to shuffle an array.

To make the concept clear, let me compare to a deck of cards. How do you prevent from drawing the same card twice? By not putting the card back in the deck before you draw another one.

You get the same result by simply shuffling the deck, and picking the next card, one by one.

shuffle is a function you can find in List::Util. You use it like this: 

use List::Util 'shuffle';
my @shuffled_deck = shuffle 1 .. 10;
local $\ = "\n";
foreach(@shuffled_deck) {
    print;
}

[download]
I get, for example, the following output: 
1
2
9
8
7
10
4
5
6
3

It'll be far more efficient than retrying until you get something you haven't seen before, especially near the end, when you've almost seen them all.

In reply to Re: How to not print the same random number by bart
in thread How to not print the same random number by Anonymous Monk

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