To distinguish between no argument and an empty array, you can use the ;\@ prototype. It makes it impossible to specify more than one argument, though: 
#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

sub mysay (;\@) {
    my ($arr) = @_;
    if (defined $arr) {
        print "$_\n" for @$arr;
    } else {
        print "$_\n";
    }
}

my @arr2 = qw( Two/1 Two/2 );
mysay(@arr2);

my @arr1 = qw( One );
mysay(@arr1);

$_ = "Don't show";
my @arr0;
mysay(@arr0);

$_ = "Underscore";
mysay();

# This doesn't compile.
# mysay(qw(a b c));

[download]
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

In reply to Re: Spotting an empty array as argument by choroba
in thread Spotting an empty array as argument by Chuma

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