You have chosen a really bad representation for sorting.

You could transform your data to an array of hashes instead:

my @persons = 
    { 
      firstname => 'name1',
      lastname  => 'lname1',
      city      => 'city1',
   },
    { 
      firstname => 'name2',
      lastname  => 'lname2',
      city      => 'city2',
   },
   ...
);
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And then sort with sort { $a->{firstname} cmp $b->{firstname} } @persons.