Similar to thor's solution above--no greps--but this one'll also wipe out the dupes from your arrays:

use strict;

my @a = (0,1,2,3,4,5,6,7,8,9);
my @b = (0,1,4);

my @isect = ();
my @diff = ();
my %count = ();

foreach my $e (@a) { $count{$e} = 1; }
foreach my $e (@b) { $count{$e} += 2; }

@a = @b = ();

foreach my $e (keys %count)
{ if ($count{$e} == 1) {push @a, $e;}
  elsif ($count{$e} == 2) {push @b, $e;}
  else {print "$e ";}
}
[download]

For a bunch of good examples of this kind of stuff, try the Perl Cookbook, recipes 4.6 & 4.8.