To create grep– or map-like syntax, you need to use Perl’s prototypes, despite whatever we told you in Understand why you probably don’t need prototypes. Perl needs the special hints that prototypes to parse a block as an argument to a subroutine. Continue reading “Make grep-like syntax”
Category: item
Profile with Devel::NYTProf
Profile before you decide where to optimize—you might be surprised where you’re losing all of your performance.
We won’t go into all the details of profiling in this Item, but you can read about those in Mastering Perl. In short, profilers count something then report the results. They can track any of the things that you might care about. The Devel::NYTProf module, like most profilers, tracks time, counting the statements you run and how long they take. Continue reading “Profile with Devel::NYTProf”
Use lookarounds to split to avoid special cases
There are some regular expression tricks that can help you deal with balanced delimiters in a string. The split command takes a pattern, removes the parts of a string that match that pattern, and give you a list of the parts of the string between those separators. Said another way, split works when the parts you don’t need are between the values. Continue reading “Use lookarounds to split to avoid special cases”
Understand why you probably don’t need prototypes
You should understand how Perl’s prototypes work, not so you’ll use them but so you won’t be tempted to use them. Although prototypes can solve some problems, they don’t solve the problems most people want. Continue reading “Understand why you probably don’t need prototypes”
Return error objects instead of throwing exceptions
Programmers generally consider two types of error communication: the “modern” and shiny exception throwing, and the old and decrepit return values. When they consider these, they choose one and forsake the other. One is good, and the other is bad. Programmers won’t agree on which is which though. Continue reading “Return error objects instead of throwing exceptions”
Use lookarounds to eliminate special cases in split
The split built-in takes a string and turns it into a list, discarding the separators that you specify as a pattern. This is easy when the separator is simple, but seems hard if the separator gets more tricky. Continue reading “Use lookarounds to eliminate special cases in split”
Enchant closures for better debugging output
When you’re using code references heavily, you’re going to have a problem figuring out which one of them is having a problem. You define them in possibly several and far-flung parts of your program, but when it comes to using them, you don’t know which one you are using. You can’t really print its value like you would for a scalar, making it more difficult for you to debug things. You can dereference a scalar or an array to see what it is, but you can’t dereference a code reference without making it do something. Continue reading “Enchant closures for better debugging output”
Normalize your Perl source
Perl has had Unicode support since Perl 5.6, which means that most Perl tutorials have been bending the truth a bit when they tell you that a Perl identifier, the name that you give to variables, starts with [A-Za-z_] and continues with [0-9A-Za-z_]. With Unicode support, you have many more characters available to you, but moving outside the ASCII range has some problems. You can’t always tell what a variable name is just by looking at it (and this is a design bug in Perl: RT 96814). For instance, you don’t really don’t know what this variable is: Continue reading “Normalize your Perl source”
Intercept warnings with a __WARN__ handler
Perl defines two internal pseudo-signals that you can trap. There’s one for die, which I covered in Override die with END or CORE::GLOBAL::die and eventually told you not to use. There’s also one for warn that’s quite safe to use when you need to intercept warnings. Continue reading “Intercept warnings with a __WARN__ handler”
Know the difference between utf8 and UTF-8
Perl actually has two encodings that get the letters u, t, f, and 8. One will happily let you do bad things, and the other will let you do bad things but with a warning that you can make fatal. Continue reading “Know the difference between utf8 and UTF-8”