use Data::Dumper;
my @list = qw/ 1 1 1 234 234 3 5 5 2 7 6 3 6 8 4 /;
my %count;
$count{$_}++ foreach @list;
print Dumper \%count;
__END__
$VAR1 = {
          '6' => 2,
          '3' => 2,
          '234' => 2,
          '7' => 1,
          '2' => 1,
          '8' => 1,
          '4' => 1,
          '1' => 3,
          '5' => 2
        };
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In the above posting, notice how the mere mention of a hash-key causes it to magically appear, with the initial value of zero, so that it can be "++" incremented to the value of one. This bit of perl-mojo is called "autovivification." Otherwise known as "do the right thing quietly and with a minimum of fuss."

No , that is not autovivification . Just like this is not autovivification

$foo++;
$bar[$_]++;
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However, when you

use strict;

writing

$foo++;

will cause perl to complain (if you have not declared (and thus created) $foo before),
while writing

$bar[396]

will cause no complaints, even if you never used this index before(or a higher one), or never told Perl how big @bar should be. You will have to declare @bar, of course. So these two examples are not comparable. And I believe the second example actually is where we see autovivication at work.