the lack of a native type system means that your classes and methods can’t be certain of the type of data they’re being passed, which forces you into a position of defensive programming

Well, in my view Perl does never force me into any position, but, depending on the task, defensive programming is recommended.

Using objects as a surrogate for a type system is just a thin layer. For safety, this only helps if the classes do the appropriate validations on object creation. For example, Venus::Number accepts any value, so my classes and methods still can't be certain of the type of data they're being passed:

use 5.028;
use warnings;
use Venus::Number;
use File::Temp;

my $n;

# These two come with warnings
say Venus::Number->new($n);                      # ''
say Venus::Number->new($n,$n);                   # 0

$n = 1;
say Venus::Number->new($n);                      # 1

$n = "abc";
say Venus::Number->new($n);                      # abc

$n = [3,2,1];
say Venus::Number->new($n);                      # ARRAY(0x...)
say Venus::Number->new($n)->abs;                 # 94653281131368

$n = File::Temp->new;
say Venus::Number->new($n);                      # /tmp/ER2Mi14BOz
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