It appears the read_multirow is returning an array of array refs. See perlreftut In short each element of @my_matrix is a *reference* to an array of values.

print "@$_\n" for @my_matrix;   # short way

for my $row_ref( @my_matrix ) { # longer way
    my @data = @$row_ref;
    print "@data\n";
}

use Data::Dumper;
print Dumper \@my_matrix;       # always good to see what data structu
+re looks like
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