Greetings,
Just to help illustrate how Perl 'flattens' or as I try to think of it (thanks to diotalevi) 'list-ifies' subroutine arguments consider the following 
#!/usr/bin/perl -w
use strict;

my @array = qw(arrayval1 arrayval2 arrayval3 arrayval4 arrayval5);
my %hash = (key1=>'val1', key2=>'val2', key3=>'val3');

sub check_input_list
{
    print "\n";
    print "@_";
    print "\n";
}

check_input_list(@array, %hash);
check_input_list(\@array, %hash);
check_input_list(@array, \%hash);
check_input_list(\@array, \%hash);

[download]
The Output 

arrayval1 arrayval2 arrayval3 arrayval4 arrayval5 key2 val2 key1 val1 
+key3 val3

ARRAY(0x1824320) key2 val2 key1 val1 key3 val3

arrayval1 arrayval2 arrayval3 arrayval4 arrayval5 HASH(0x182435c)

ARRAY(0x1824320) HASH(0x182435c)

[download]
Notice in the output of the first call the keys and values from %hash get tacked onto the end of the values in @array as if the entire thing were one huge list. Now imagine trying to get keys or values from %hash? Not likely nor easy.
In the second and third examples we pass one reference but the argument list is still just a list.
The final example is much cleaner. If you were confused about what you originally passed into the sub your could always call ref and find out; otherwise there is no way to tell if you are passed a 'list-ified' hash or array.

-InjunJoel
"I do not feel obliged to believe that the same God who endowed us with sense, reason and intellect has intended us to forego their use." -Galileo

In reply to Re^2: Small troubles with references by injunjoel
in thread Small troubles with references by coldmiser

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.