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    <p>I think you are mixing 'defined' and 'declared' concepts.</p> <p>Your are asking for 'How to check if variable is declared in perl' but then you are checking if a variable is defined. These are two different concepts.</p> <p>In perl if you use <em>'use strict'</em> you are automatically checking for any variable <strong>not declared</strong> (using <strong>my</strong>, <strong>local</strong> or <strong>our</strong>). Once you have a variable declared, you can test if it is defined (have a value assigned).</p> <p>So in your test, you are missing a prior declaration before testing for defineness</p> <pre><code>use strict; my $x; # you are missing this part [...] | # code # your test for define print defined $x? "defined\n" : "not defined\n"; </code></pre> <p>Please be aware the testing for only $x is incorrect for your purpose:</p> <pre><code>my ($x,$y, $z); $w; # not declared (use strict will catch it and die) $x = 0; # declared and defined BUT if you make a logic test like 'if ($x) {}' then it will be FALSE, so don't confuse testing for **'$x'** and testing for **'defined $x'** $y = undef; # declared but not defined $z = 1; # declared, defined, and logial test TRUE </code></pre> <p>Finally the answer of xenorraticide seems faulty to me: he suggest <strong>'unless $x' that is not correct</strong> for testing if defined as I said before. He also suggest <strong>'unless exists $x', that is wrong for testing scalars</strong>. 'exists' test is only for hashes keys (and deprecated for arrays).</p> <p>Hope this helps.</p>
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    1. USPablo Marin-Garcia
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