Another reason to avoid /^$/ is that it non-intuitively matches a single newline:

#!/usr/bin/perl -wT
use strict;

# only one one of these is an "empty" string right?
my @arr = ("", "\n", "dog", "cat");  

my @haslength = grep {length} @arr;
my @notempty  = grep {!/^$/} @arr;

print scalar @haslength, " members have length\n";
print scalar @notempty,  " members are not \"empty\"\n";

__END__

=head1 OUTPUT
3 members have length
2 members are not "empty"
[download]

So, /^$/ actually classifies a single newline as an "empty" string.... Sometimes thats what you want, but it isn't usually what people expect.

-Blake