Yes it is. Your @fruits "array" consists of one element, the string "Apple Banana Cherry Honeydew Watermelon", so there is nothing to join.

If you intended for @fruits to contain 5 elements, then you need to split it up on assignment. The easiest way to do that is to change your first line to my @fruits = qw/Apple Banana Cherry Honeydew Watermelon/;

update: see http://perldoc.perl.org/perlop.html#Quote-Like-Operators for the qw// quote-like operator. Alternately, use split to break up the string into multiple elements.