Paladin has already shown that you could have found your error yourself if you had used the pragmas "strict" and "warnings". Also note that a little extra whitespace to align your array definition can make it easier to read. That alone can help to avoid errors in accessing them.

use strict;
use warnings;
my @ar1 = (
    ["one",   "two",          ],
    ["three", "four", "five", ],
);
my $count = scalar @{ $ar1[1] };
print "count = $count\n";
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