When you have sorted out your single print variant you may be interested in this three print variant

use strict;
use warnings;

my @lines = map {(substr ' ' x 15, 0, 15 - $_) . ('@' x (2 * $_)) . '@
+'} (0..4);
print join "\n", @lines, '';
print ' ' x 10, '@' x 11, "\n";
print join "\n", reverse @lines;
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Prints:

               @
              @@@
             @@@@@
            @@@@@@@
           @@@@@@@@@
          @@@@@@@@@@@
           @@@@@@@@@
            @@@@@@@
             @@@@@
              @@@
               @
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