On Fri, Apr 24, 2009 at 3:53 PM, Chas. Owens <chas.ow...@gmail.com> wrote: > 2009/4/24 Jay Savage <daggerqu...@gmail.com>: > snip >>> Hmm, I don't think it would reparse the whole file, but >>> it does run in a BEGIN block...hmm, I must test it. >>> >> >> It runs in a begin block, but it is still lexically scoped. Pragmata >> are very special cases of modules that provide modifications of >> compile-time behavior, and many of them perform sleight of hand behind >> the scenes. Here, the sleight of hand is using utf8 to simply add a >> bit mask to $^H and relying on the the behavior of the compiler hints. >> >> The important thing to remember about a BEGIN block that it is run as >> soon as it is defined, where it is defined. Just because it is >> executed early in the compile->optimize->run cycle does not mean that >> it is magically transported to an earlier position in the file. >> Generally, you want to apply the behavior introduced by a module to >> have file scope, which is why use statements normally appear early in >> the file. >> >> See perlpragma and the description of $^H in perlrun for details. > snip > > All of this is good information, but for one thing: not all pragmas > are lexically scoped. Hence the need to test and/or read the docs. > For instance, the re pragma[1] is only partially lexical: > > #!/usr/bin/perl > > use strict; > use warnings; > > "foo" =~ /(o+)/; #re 'debug' still affects this line > > use re 'debug'; > > 1. http://perldoc.perl.org/re.html >
Agreed, absolutely. My point was that just because something's wrapped in in a BEGIN block doesn't mean one should assume it affects the entire program, or be surprised when it doesn't --j -------------------------------------------------- This email and attachment(s): [ ] blogable; [ x ] ask first; [ ] private and confidential daggerquill [at] gmail [dot] com http://www.tuaw.com http://www.downloadsquad.com http://www.engatiki.org values of β will give rise to dom! -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
