use strict;

{
    package Calculator;
    use List::Util qw/reduce/;
    sub add      { reduce { $a + $b } @_ }
    sub multiply { reduce { $a * $b } @_ }
}

{
    package main;
    use Test::More tests => 2;
    
    # Calculate the fifth triangular number
    is(
        Calculator->add(1 .. 5),
        15,
        );
    
    # Calculate five factorial
    is(
        Calculator->multiply(1 .. 5),
        120,
        );
}

[download]
perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

In reply to Spot the deliberate mistake - list-based maths by tobyink

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