What do you get if you evaluate a hash in scalar context?

Question

Consider the following snippet:

use strict;
use warnings;

my %a = ( a => 1,
          b => 2,
          c => \'cucu\',
          d => undef,
            


        

Answer 1

To focus too much on this fractional pattern (as an indicator for internal details of the hash), can be confusing. There is an aspect of the "scalar value" of a hash that is important for potentially every Perl program and that is, if it is considered true in Boolean context, see an example:

if (%h) {
    print "Entries in hash:\n";
    for my $k (sort keys %h) {
        print "$k: $h{$k}\n";
    }
}

In perldoc perldata, section Scalar-values, you can read that

[...] The Boolean context is just a special kind of scalar context where no conversion to a string or a number is ever performed.

and, some paragraphs later,

If you evaluate a hash in scalar context, it returns false if the hash is empty. If there are any key/value pairs, it returns true [...]