c:\@Work\Perl\monks>perl -wMstrict -le
"use Data::Dump qw(dd);
 ;;
 use constant INITIALIZER => '';
 ;;
 my @strings = (INITIALIZER) x 6;
 dd \@strings;
 ;;
 @strings[1, 4] = qw(foo bar);
 dd \@strings;
 ;;
 my @empties = grep { $strings[$_] eq INITIALIZER } 0 .. $#strings;
 print qq{indices of empty elements: @empties};
"
["", "", "", "", "", ""]

["", "foo", "", "", "bar", ""]

indices of empty elements: 0 2 3 5