why would insist on sticking the information in the while loop conditional check instead of a variable?

Variables can help you clarify what you code does. Something an obscure data structure does not. For example,

my $DEBUG = 1;

#... later in your code
if ($DEBUG) { warn "Something happened\n" }
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I bet your thinking that this is pretty obvious but I still want to reduce the number of variables.

If you think you have too many variables in a section of code, chances are you have not abstracted out it out enough. Move more of your code into other subroutines to enhance clarity.

my $dimensions = _get_dimensions_for(5,8);

while (my ($r,$s) = each %{ $dimensions } ) {
    print($r);
}
sub _get_dimensions_for { 
  my $x = shift;
  my $y = shift;

  return { 
    x=> $x, 
    y=> $y 
  } 
}
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Note: Thanks to ikegami for pointing out my error.

Doesn't your snippet still suffer from the problem?

I have a slight preference for omitting variable names if I don't really need them.

If you are concerned about cluttering up a (possibly over-broad) scope with needless nonce variable names (not an entirely unreasonable concern, IMO), why not just enclose the sub-section of code in its own limited sub-scope?

>perl -wMstrict -le
"{ my %h = qw(a 1  b 2  c 3);
   while (my ($k, $v) = each %h) {
     print qq{$k -> $v};
     }
   }
"
c -> 3
a -> 1
b -> 2
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why not just enclose the sub-section of code in its own limited scope?

Simply for reason of aesthetics ;-)

As was already pointed out, there are many ways to skin the cat. I was just wondering whether Perl language really dictates us here to introduce a variable name, since in all other cases I can think of, an expression which is only needed once, doesn't need to be named. Having found this case where I could not do without introducing a variable, I considered it more likey that I was just missing some feature of Perl...
-- 
Ronald Fischer <ynnor@mm.st>