...although, what do they mean by "constant expression?"
Yeah, good question. Constant expression means whatever perl constant-folds at compile time. Numeric and string literals are constant, most simple operators (arithmetic and logic and things like that, but not including x) are constant-folded iff all their arguments are constants, and so are a few named builtins like uc, most other expressions aren't. There are some corner cases (like the comma operator) and even some version differences, so if you want to know for sure what's constant-folded and what isn't, you may need to dump the code with use O "Deparse"; or even use O "Concise";. If in doubt, just compare to $. explicitly if you want that semantics.
There are at least two other cases where an expression being constant matters in how your perl code is interpretted, though one of these might be a bug: Twin-lines japh and Re^3: A cleaner way of scoping variables.
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.
|