note
Athanasius
<p>Hello [ghosh123],</p>
<p>[LanX] has [id://1011259|explained] the syntax of the expression, but you may be wondering, why create a hash reference only to immediately dereference it?</p>
<p>A solution using a third, named hash is more straightforward:</p>
<code>
my %hash3 = (%hash1, %hash2);
my @uniq = keys %hash3;
</code>
<p>But what happens if we want to eliminate the named hash? The obvious approach:</p>
<code>
my @uniq = keys (%hash1, %hash2);
</code>
<p>doesn’t work, because the Perl interpreter sees only a simple list. So it’s necessary to tell the interpreter to create a <i>hash</i>, but the only syntax for this that doesn’t involve another named hash is curly braces <c>{}</c>, which creates a hash as required but returns a <i>reference</i> to it. Hence the need for the more complicated syntax which creates the hash reference and then dereferences it.</p>
<p>Actually, however, this isn’t necessary in Perl 5.14 or later, because [doc://keys] can now also take a hash reference as its argument:</p>
<code>
#! perl
use Modern::Perl;
use Data::Dump;
my %hash1 = (fred => 'wilma', barney => 'betty');
my %hash2 = (homer => 'marge', fred => 'wilma');
my @uniq = keys { %hash1, %hash2 };
dd @uniq;
</code>
<p>Output:</p>
<code>
23:05 >perl 464_SoPW.pl
("barney", "homer", "fred")
23:08 >
</code>
<p>Hope that helps,</p>
<div class="pmsig"><div class="pmsig-968231">
<p>
<table width="100%">
<tr>
<td align="left">
Athanasius <font color="#008000"><</font>[href://http://www.biblegateway.com/passage/?search=John%203:16&version=NLV|<font color="#008000">°</font>]<font color="#008000">(((><</font> <i>contra mundum</i>
</td>
<td align="right">
[href://http://translate.google.com.au/#la/en/Iustus%20alius%20egestas%20vitae%2C%20eros%20Piratica%2C|<b>Iustus alius egestas vitae, eros Piratica,</b>]
</td>
</tr>
</table>
</p>
</div></div>
1011256
1011256