($first,$second) = ($second,$first);
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                - Ant
                - Some of my best work - Fish Dinner

No way! You are saying that all I have to do is:


($first,$second) = ($second,$first);
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and it automatically exchanges them for you?

Is there any other ways of doing this that might be used for other tasks? Or is this the only *reasonable* way to do it?

Mr.T
qw/"I pity da foo' who don't use Perl!"/;

Asigning an array to a list of variables is a common way to give meaning full names to the items in an array. You can use it to make handling the returns of functions like local time easyer.
IE:
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time); as opposed to
@time = localtime(time); and having to remeber that $time[2] is the hour.

If you have an array in the list on the left side of the = it will gobble up all the remaing items in the array on the right side. You need to be careful of this, because anything following the array will not have anything asigned to it.
IE:
($one, $two, @three, $four) = ('one', 'two', 'three', 'four'); $one will equal 'one'
$two will equal 'two'
@three will equal ('three', 'four')
and $four will be undefined

There are many ways to use this feature of perl.
You will probably see

sub do_stuff {
    my ($foo, $bar) = @_;
}
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to get the arguments sent to a subroutine into named variables often.

This is otherwise known as DWIM, Do What I Mean.

Cool aint it?

Basically, whenever you assign to a list, each element gets assigned to, all in parallel. So, in parallel, the value of the first gets assigned to the second, and the value of the second (which isn't *yet* the previous value of the first) gets assigned to the first; thus, they get exchanged. See?

re: Is there any other ways of doing this that might be used for other tasks? Or is this the only *reasonable* way to do it?

You might want to ask that in the Obfuscation section and then stand back.

how about:

push @INC, $first, $second; # not a temporary since it already exists!
$_= pop @INC foreach ($first, $second);
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You can do that... I believe it has something to do with perl creating a temporary anonymous array... but I am not entirely sure...

                - Ant
                - Some of my best work - Fish Dinner

$a = $a ^ $b;
$b = $a ^ $b;
$a = $a ^ $b;
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First of all $a and $b are special in Perl so it is a good idea to avoid using them, even for throw-away variables.

That aside, this method of swapping data is unreliable. Witness:

my $x = ["hello"];
my $y = ["world"];

print "We have \$x=$x and \$y=$y.\n";
print "The first element of \$x is '$x->[0]'\n";
print "The first element of \$y is '$y->[0]'\n";
print "Now swapping...\n";

$x = $x ^ $y;
$y = $x ^ $y;
$x = $x ^ $y;

print "We have \$x=$x and \$y=$y.\n";
print "The first element of \$x is '$x->[0]'\n";
print "The first element of \$y is '$y->[0]'\n";
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What happened, of course, is that you stringified the object and so lost the reference.

Now if you want a sneaky way to swap variables, the following takes a list of variables as arguments and rotates them. The first goes to the end, the rest move forward one. With 2 variables this just swaps.

my $x = ["hello"];
my $y = ["world"];

print "We have \$x=$x and \$y=$y.\n";
print "The first element of \$x is '$x->[0]'\n";
print "The first element of \$y is '$y->[0]'\n";
print "Now swapping...\n";

rotate($x, $y);

print "We have \$x=$x and \$y=$y.\n";
print "The first element of \$x is '$x->[0]'\n";
print "The first element of \$y is '$y->[0]'\n";

# And here is the magic bit
sub rotate { @_[0..$#_] = @_[1..$#_, 0]; }

# BTW here is something that won't work.  Lists are not arrays! :-)
sub wont_rotate { @_ = @_[1..$#_, 0]; }
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I think I understand, but I am not exactly sure what the '^' operator does. Please forgive my ignorance, but what does it do, and what is it called? (In Perl.)

Mr.T
qw/"I pity da foo' who don't use Perl!"/;

It should be clear by now, but for completeness sake I add

($one, $two, $three, $four) = ($three, $one, $four, $two);

# and array slicing
my @arr = qw/one two three four/;
@arr = @arr[2,0,3,1];
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-- Hofmator

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