my $op = shift @ARGV;
if ( $op eq 'add' ) {
    my $rtn = add( @ARGV );
    print "The sum is: $rtn\n";
} elsif ( $op eq 'multiply' ) {
    my $rtn = multiply( @ARGV );
    print "The product is: $rtn\n";
}

##</code><code>##

sub add {
    my $sum = 0;
    for ( @_ ) {
        $sum += $_;
    }
    return $sum;
}

##</code><code>##

sub add {
    my $sum = 0;
    $sum += $_ for @_;
    return $sum;
}

##</code><code>##

#!/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};

##</code><code>##

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

my $op = shift @ARGV;
my $result;
$op eq 'add' ?
    ( $result = 0, map { $result += $_ } @ARGV ) :
    ( $result = 1, map { $result *= $_ } @ARGV );
print ( $op eq 'add' ? 'The sum is:' : 'The product is:' );
print " $result\n";