Are you sure? Consider:

use strict;
use warnings;
use Data::Dump::Streamer;

my $value = undef;

print !!$value;

my $nothing = nothing ();
my $retNothing = retNothing ();
my $retUndef = retUndef ();
my $retFalse = retFalse ();
my $retFalse2 = -retFalse ();

Dump (\$nothing);
Dump (\$retNothing);
Dump (\$retUndef);
Dump (\$retFalse);
Dump (\$retFalse2);


sub nothing {
}

sub retNothing {
    return;
}

sub retUndef {
    return undef;
}

sub retFalse {
    return 1 == 0;
}

[download]

Prints:

$SCALAR1 = \do { my $v = undef };
$SCALAR1 = \do { my $v = undef };
$SCALAR1 = \do { my $v = undef };
$SCALAR1 = \do { my $v = '' };
$SCALAR1 = \do { my $v = 0 };

[download]

Updated to add two false cases

and in list context :)

...

my @nothing = nothing ();
my @retNothing = retNothing ();
my @retUndef = retUndef ();
my @retFalse = retFalse ();
my @retFalse2 = -retFalse ();

Dump (\@nothing);
Dump (\@retNothing);
Dump (\@retUndef);
Dump (\@retFalse);
Dump (\@retFalse2);

...

[download]

Prints:

$ARRAY1 = [];
$ARRAY1 = [];
$ARRAY1 = [ undef ];
$ARRAY1 = [ '' ];
$ARRAY1 = [ 0 ];

[download]
DWIM is Perl's answer to Gödel

In reply to Re^3: Elegant way to return true or nothing from a subroutine? by GrandFather
in thread Elegant way to return true or nothing from a subroutine? by Anonymous Monk

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.