Random remailing script had. Help.

Thanks to Alan Barrett who sent me a script to get me started with. I have
two questions still.

1) Why not just $second = rand ($#remailers+1), instead of the two line
   $second routine? (And why did I have to add the +1...).

2) How do I output the variables as csh environmental variables that stick
   around after the perl script has executed? I usually use 'setenv' but perl
   didn't like that.

Here is Alan's script, edited a bit by me:

#!/usr/bin/perl

# given a set of remailers, choose two of them at random.
# repeat this operation five times.
# output the resulting list of 10 remailers.


#
# here's the list of remailers to be considered.
# make it as long or as short as you like. (but no shorter than 2 entries!)
#
@remailers = ("One", "Two", "Three", "Four" , "Five", "Six");

#
# seed the random number generator.
# this is not a strong PRNG!
#
srand(time);

foreach $cycle (1..5) {

    # choose random remailers
    $first = rand($#remailers+1);
    $second = rand($#remailers);
    $second++ if $second >= $first;

    # output the choices
    print $remailers[$first],"->",$remailers[$second],"\n";
}

And a few outputs:

Four->One
One->Six
One->Six
Five->Three
Four->Two

One->Four
One->Five
Six->Four
Five->Two
One->Six

Five->Two
Two->Five
Five->Three
Five->Four
Five->Five

I may have screwed it up, as Alan originally had no +1 in the $first line,
and had -1 in the next line, but it never outputed "Six" then.

Background: One-Six will be addresses of Cypherpunk remailers and I am sending
packages of five e-mails (~40K each) to many people a day. I figured why not
appease you guys by helping with the traffic, but do it randomly and chain
off two remailers per e-mail. I want csh variables though, as output. How do
I get these, or how to I fetch the perl variables for a Unix command line
(I am currently using 'setenv name value' then putting $name into a Unix
command)?

-Xenon
P.S. If you wish to e-mail answers (slow!) use na38138@anon.penet.fi.

Xenon refers to the random choice script I sent him, and asks:

>>     # choose random remailers
>>     $first = rand($#remailers+1);
>>     $second = rand($#remailers);
>>     $second++ if $second >= $first;

> 1) Why not just $second = rand ($#remailers+1), instead of the two line
>    $second routine? (And why did I have to add the +1...).

If there are N remailers, then $#remailers will be N-1.  (It's the value
of the last index into the array, but the array starts at zero.)
rand($#remailers+1) is a floating point number in the range [0,N)
(including 0, but not including N).  Hey, we're missing some int()
operations here; it should be like this: 

>>     # choose random remailers
>>     $first = int(rand($#remailers+1));
>>     $second = int(rand($#remailers));
>>     $second++ if $second >= $first;

Now, $first is an integer in the range [0,N-1], which is correct for
indexing into the array of available remailers.  When it comes to choosing
$second, we do not want to choose the same value as $first; for example,
if N is 5 then we want to choose $first from the set {0,1,2,3,4}, and if
we happen to choose $first=2 then we want to choose $second from the set
{0,1,3,4}.  The two-line calculation of $second will do that. 

> 2) How do I output the variables as csh environmental variables that stick
>    around after the perl script has executed? I usually use 'setenv' but perl
>    didn't like that.

You will have to have csh parse the output of the perl script.  For
example, have the perl script print some csh-compatible "setenv" commands,
with something like

    print "setenv A$cycle $remailers[$first]\n";
    print "setenv B$cycle $remailers[$second]\n";

and have the csh script execute the perl script and parse its output
using something like this:

    eval `perl perl-script`

BTW, don't ever write csh scripts.  See Tom Christiansen's periodic FAQ
posting in comp.unix.shell. 

> I may have screwed it up, as Alan originally had no +1 in the $first line,
> and had -1 in the next line, but it never outputed "Six" then.

That was a bug, which you fixed.

--apb (Alan Barrett)