use strict;
use warnings;
use 5.010;

my $string = "HELLO\nWORLD\nGOODBYE";


my @patterns = (
    '\A (.)',       #Match start of entire string followed by any char
    '^ (.)',        #Match start of every line followed by any char
    
    '(.) \z',     #Match any char followed by end of the entire string
    '(.) $',      #Match any char followed by end of a line
);

for my $pattern (@patterns) {
    my @matches =  $string =~ /$pattern/gxms;
    say "@matches";

    say '*' x 20;
}


--output:--
H
********************
H W G
********************
E
********************
O D E
********************

##</code><code>##

use strict;
use warnings;
use 5.010;

sub do_stuff {
    my @x = shift;
    my @y = shift;

    say "@x";
    say "@y";
}

my @arr1 = (10, 20);
my @arr2 = ('a', 'b');

do_stuff(@arr1, @arr2);

##</code><code>##

do_stuff(10, 20, 'a', 'b');

##</code><code>##

my @x = 10;
##</code><code>##

my @x = (10);