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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