use warnings;
use strict;
my @x = (1,2,3);
our ($a,$b,$c);
(*a,*b,*c) = \(@x);
$a = "f";
$b = "o";
$c = "o";
print sort {$b<=>$a} qw(17 11 13 29 31 37 3 2 7 5 19 23);
print @x; 

##</code><code>##

$ perl -le 'my $a=1; print sort {$b<=>$a} 1'
Can't use "my $a" in sort comparison at -e line 1.