#!perl -w
@nums = 100000 .. 999999; # Generate all the possible numbers

## Shuffle them (use a better rand if needed)
$_ ne ($a=int( rand( $#nums-$_+1))+$_) and $nums[$_] ^= $nums[$a] ^= $nums[$_] ^= $nums[$a] for (0..$#nums);

print pop@nums; # pop a new one each time you need it

##</code><code>##

#!perl -w
@nums = 100000 .. 999999; # Generate all the possible numbers

## Shuffle them (use a better rand if needed)
$_ ne ($a=int( rand( $#nums-$_+1))+$_) and $nums[$_] ^= $nums[$a] ^= $nums[$_] ^= $nums[$a] for (0..$#nums);
open OUT, '>randoms' or die $!;
print OUT pack 'I*', @numbs;
close OUT or warn $!;

##</code><code>##

....
open RNDNUM, '<randoms' or die $!;
binmode(RNDNUMS); # If needed!
seek RNDNUMS, -4, 2;
my $newlen = tell RNDNUM;
my $rndnum = do {
     local $/=\4; 
     unpack 'I',<RNDNUM>;
}
truncate RNDNUM, $newlen or die $!;
close RNDNUM or warn $!;
.....
# do whatever with $rndnum