note moritz <p>In this specific case, supplying an import list (the <c>qw/is_valid/</c> part) imports that symbol, leaving it out imports nothing.</p> <p>In the general case, the import list is passed to the loaded module's <c>->import</c> function, and it can do whatever it wants to do.</p> <p>But many, many modules are based on [mod://Exporter]. For Exporter-based modules, not specifying an import list gets you all the symbols listed in the default exportation list called <c>@EXPORT</c>. Specifying an import list disables that default, and instead gives you the symbols you asked for, if they are listed in <c>@EXPORT_OK</c>. If they are not, you'll get an error.</p> <p>In most cases, importing doesn't affect performance to any discernible degree, but it is often easier for maintenance to list exactly the symbols you want to import. If you have many <c>use</c> statements, it's easy to search for which module gave you a particular symbol.</p> <p>But it is worth mentioning that a few peculiar modules (if I remember correctly, [mod://POSIX] and/or [mod://CGI]) have quite many symbols, and only compile the routines to be exported as requested. In this case, it can make a noticeable difference in start-up time if you import all routines.</p> <!-- Node text goes above. Div tags should contain sig only --> <div class="pmsig"><div class="pmsig-616540"> [http://perl6.org/|Perl 6 - the future is here, just unevenly distributed] </div></div> 1015838 1015838