Another way, using the perl rand function,

@nums = '0' .. '30'; # change to '000000' .. '999999';
srand;
while(@nums){
    push(@randnums, splice @nums,int(rand @nums),1);
}
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If you want to be able to interrupt the process, you could choose to write @nums to a file, reload it and continue.

# Test print:
print join(' ',@randnums);
print "\n";
print join(' ',sort {$a <=> $b} @randnums);
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