I also used to code in Pascal (never mind how long ago). If I was swapping two numerics, I used the XOR function. Here's the Perl version (since we ain't Pascal Monks):

$a = 598;
$b = 77;
$a = $a ^ $b;
$b = $a ^ $b;
$a = $a ^ $b;
print "$a $b\n";
[download]

Use the ($a,$b) = ($b,$a) version, though. I just put this up for fun: TMTOWTDI!

- robsv

Update: Aaargh! Ignore me. dailylemma posted this already. That's what I get for starting a reply, going for a soda, then finishing the reply.