in reply to Difficulty in randomization

Considering that 10 is much smaller than 600, I'd do: 
my @array = ('-') x 600;
foreach (1 .. 10) {
    my $i = int rand 600;
    redo if $array[$i] eq 'X';
    $array[$i] = 'X';
}
my $joined_string = join "", @array;

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In theory, this may run "for ever", but in practice it will run fast enough.

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Re^2: Difficulty in randomization
by jwkrahn (Abbot) on Mar 05, 2012 at 00:28 UTC

    Same thing without the array: 

    my $joined_string = '-' x 600;
foreach ( 1 .. 10 ) {
    my $i = int rand 600;
    redo if 'X' eq substr $joined_string, $i, 1;
    substr $joined_string, $i, 1, 'X';
}

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[d/l]

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