And since we're nitpicking, your (the original poster's) use of @pack as a global variable is bad form:

#!/usr/bin/perl

use Dog;

my @pack = create_dogs(15);

sub create_dogs #of course, this should possibly be a method of Dog, b
+ut whatever
{
  my $num = shift;
  map Dog->new, 1 .. $num; # or 0, whichever makes you happy.
}
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