I don't understand the purpose of the @Data + 0; statement in your code examples. Could you please explain? (Note that they produce "Useless use of addition (+) in void context at ..." warnings if warnings are enabled.)
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According to the camel book, that's a way to force an array to a scalar context. Their example is
@days + 0; # implicitly force @days into a scalar context
I'm afraid I don't understand it any more than that.
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The thing to realize about the @Data + 0; statement in your reply above is that it forces the evaluation of @Data in scalar context (yielding the number of elements) and then throws away the result!
All of these statements are equivalent:
my $n = 0 + @Data;
my $n = scalar @Data;
my $n = @Data;
In the first two, the scalar operation and the use of the scalar built-in on the right hand side of the assignment are redundant because the scalar assignment itself supplies all the scalar context that is necessary. (The usage
my $n = scalar @Data;
is sometimes advanced as a best practice for reasons of maintainability: supposedly, it makes crystal clear your intention to get the number of elements of the array.)
Where forcing scalar context through a null scalar operation or the use of scalar can be useful is in a situation in which the overall context is list, such as in the argument list of the print built-in:
c:\@Work\Perl>perl -wMstrict -le
"my @Data = qw(foo bar baz);
;;
print 'hoo ', @Data, ' ha';
print 'fee ', 0 + @Data, ' fie';
print 'hic ', scalar @Data, ' hoc';
"
hoo foobarbaz ha
fee 3 fie
hic 3 hoc
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