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POTrying to localize an outside package variable through a lexical binding in Perl
 

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    <p>It's a long title, but I'm afraid I can't take a single word out without losing the true meaning of the question. I'll give a quick description of what I'm trying to achieve first, then a long rambling on why I want it done this way. Skip the rambling if you intend to directly answer abiding with the question title :-)</p> <h2>Quick description</h2> <p>Assuming the existence of a <code>lexicalize</code> builtin that does just what I want, here goes:</p> <pre><code>package Whatever; { lexicalize $Other::Package::var; local $var = 42; Other::Package-&gt;do_stuff; # depends on that variable internally } </code></pre> <h2>Whys and whynots</h2> <p>For a bit of context, I'm whitebox-testing a third-party module.</p> <p>I want the variable <strong>localized</strong> because I want it changed for a limited time only, before the tests move on to something else. <code>local</code> is the best way I found to do this without depending on knowing the module's choice for an initial value.</p> <p>I want a <strong>lexical binding</strong> for two main reasons:</p> <ol> <li>I don't want to pollute the test file's higher-level namespace.</li> <li>I want something shorter than the fully-qualified name. It's not in the sample code for brevity, but I use the identifier a lot more than what's shown, with calculations and updates relative to its previous value.</li> </ol> <p>I couldn't decently use <code>our</code> because it won't grab a variable from another package: “No package name allowed for variable $Other::Package::var in "our".” Cheating to temporarily enter Other::Package's scope doesn't cut it: if I use a block (<code>{ package Other::Package; our $var }</code>) then the binding doesn't last long enough to be useful; and if I don't (<code>package Other::Package; our @var; package main</code>) then I need to know and copy the previous package's name, which prevents moving that piece of code around too much.</p> <p>While doing my homework before asking a previous form of this question, I discovered <code>Lexical::Var</code>, which seemed like it would be <em>exactly</em> what I needed. Alas: “Can't localize through a reference.”</p> <p>I've also tried my best on my gut feeling of <code>my *var</code>-based forms, but kept bumping into syntax errors. I've learned more than I cared to about scoping and binding today :-)</p> <p>I can't think of a reason why what I want shouldn't be possible, but I can't find the right incantation. Am I asking for an unfortunate unimplemented edge case?</p>
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