c:\@Work\Perl\monks>perl -wMstrict -le "use Data::Dump qw(dd); ;; use constant INITIALIZER => ''; ;; my %strings = map { $_ => INITIALIZER } 0 .. 5; dd \%strings; ;; @strings{1, 4} = qw(foo bar); dd \%strings; ;; my @empties = grep { $strings{$_} eq INITIALIZER } keys %strings; print qq{keys of empty values: @empties}; " { "0" => "", "1" => "", "2" => "", "3" => "", "4" => "", "5" => "" } { "0" => "", "1" => "foo", "2" => "", "3" => "", "4" => "bar", "5" => "" } keys of empty values: 3 0 2 5