#!/usr/bin/perl --
use strict;
use warnings;

my $op = shift @ARGV;
my %ops = (
    'add' => sub { my $s = 0; $s += $_ for @_; print "The sum is: $s\n" },
    'multiply' => sub { my $p = 1; $p *= $_ for @_; print "The product is: $p\n" }
);

$ops{$op}(@ARGV) if exists $ops{$op};