what sort of magic is that ?

$sth->execute_array({ ArrayTupleStatus => \my @tuple}) or die $sth->errstr;

It depends on which portion of that line seems like "magic" to you.

• LanX answered with the execute_array description.
• ArrayTupleStatus is described in the DBI bind_param_array and execute_array documentation.
• \my @tuple syntax is shown in the examples of that DBI documentation. The concept of creating an array and immediately getting a reference to that array is described in perlref: Assigning-to-References, and is essentially shorthand for calling my @tuple; in one line and then using \@tuple in the execute_array() call to pass the reference to the function. (This is my best guess as to what you would consider the "magic" portion of that line of code.)
• or die $sth->errstr is the typical way to raise an error with DBI, unless you use RaiseError

https://metacpan.org/pod/DBI#execute_array

Execute the prepared statement once for each parameter tuple (group of values) provided ... by prior calls to "bind_param_array" , ...

You and me both....

But it works...