Autovivification, although a great feature, might bite you when you don’t expect it. I explained this feature in Understand autovivification, but I didn’t tell you that there’s a way to control it and even turn it off completely. The autovivification pragma, which you can get from CPAN, lets you decide how autovivification works, or doesn’t [...]
If you are playing with Unicode, you’re probably going to want to convert to the various normalization forms. There are some programs to do this in the Unicode::Tussle distribution, but you can also create some one-liners to do this as well (Item 120. Use Perl one-liners to create mini programs). If you want to read [...]
The perl interpreter is getting much better with its Unicode support, but that doesn’t mean everything just works because most of the code you probably are about is in modules, which might not have kept up. Some of this becomes apparent when you give another module some Unicode strings for it to output. For instance, [...]
Unicode character ranges have the same gotchas as the ASCII character ranges, although they become more apparent and more important. You’re probably used to creating a range for all the letters, like the character classes [A-Z] or [a-z], the range ‘a’ .. ‘z’, or the range in a transliteration, and not having a problem. If [...]
Perl 5.16 makes the Perl special variable, $$, writeable, but with some magic. That’s the variable that holds the process ID. Why would you ever want to do that? There’s not much to write about with this new feature, but there’s plenty to write against it since it introduces more magic (see commit 9cdac2 on [...]
Are you tired of adding the same modifiers to all of your regular expressions? For instance, if you might always add the /u modifier to turn on Unicode semantics on all of your patterns, including qr//, m//, and s///. Instead of remembering to do that to every pattern, the re that ships with Perl 5.14 [...]
If you need to work with Unicode strings, you probably don’t want to use Perl’s built-in string manipulation functions. This might seem a strange thing to say about a lnaguage whose main feature is string processing, but it’s a consequence of Perl’s ease in string processing. Consider what a string is. Think of that for [...]
Errors from a string eval can be tricky to track down since perl doesn’t tell you where the eval was. It treats each of the string evals as a separate, virtual file because it doesn’t remember where the string argument came from. Since perl compiles that during the run phase (see Know the phases of [...]
Perl 5.10 introduced the given-when feature, a fancier version of the C switch feature. However, it was poorly designed and tested and depended on two other dubious features, the lexical $_ and smart-matching. Parts of this feature are salvageable, but you should avoid the literal given (and probably the lexical $_ and the smart matching, [...]
Perl lets you override the effects of warn and die by redefining the signals that Perl sends when you call those functions. You probably don’t want to use the signal from die, though, since it might mean a couple of different things. You handle these special signals by setting values in the %SIG hash just [...]
