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Re (tilly) 3: No excuses about not using CGI.pm

by tilly (Archbishop)
on May 04, 2001 at 00:25 UTC ( #77763=note: print w/ replies, xml ) Need Help??


in reply to Re: Re: No excuses about not using CGI.pm
in thread variables not posting?

Actually in general I consider avoiding unexpected prototype conversion a good thing. In which case having a good way to silently ignore unwanted prototypes (and trust me, I rarely want them) is a good thing!


Comment on Re (tilly) 3: No excuses about not using CGI.pm
Re: Re (tilly) 3: No excuses about not using CGI.pm
by MeowChow (Vicar) on May 04, 2001 at 00:53 UTC
    But it's not silent (under -w):
    mysub(1); BEGIN { package Foo; require Exporter; @ISA = qw(Exporter); @EXPORT = qw(mysub); sub mysub ($) { print "mysub: @_\n" }; } BEGIN { Foo->import(); } ## Output main::mysub() called too early to check prototype at C:\Projects\GPerl +\Test\g1.pl line 1. mysub: 1
    Though I don't quite understand, if BEGIN blocks are executed before the rest of the containing file is parsed (so sayeth perlmod), why does this happen at all?
       MeowChow                                   
                   s aamecha.s a..a\u$&owag.print
      You got it in the wrong order. You can't execute a BEGIN block before you compile it, and you compile it in the order in the file. So you've compiled the lone mysub at the top, then you compile the first BEGIN block, then execute it, then compile the second BEGIN block, then execute it and OOPS! there's the problem.

      Put the lone mysub at the bottom of the file, and it'll be all good.

      -- Randal L. Schwartz, Perl hacker

        Right, I was commenting on tilly's statement that reversing the order is a good way to silently ignore the prototype.

        However, I wonder if the documentation in perlmod should be revised from:

        A BEGIN subroutine is executed as soon as possible, that is, the moment it is completely defined, even before the rest of the containing file is parsed.
        To something like:
        A BEGIN subroutine is executed as soon as possible, that is, the moment it is completely defined, even before subsequent code is parsed, but after the code before it is parsed and compiled.
           MeowChow                                   
                       s aamecha.s a..a\u$&owag.print
      It is silent for me in 5.005_03.

      But try the following:

      mysub(1); BEGIN { package Foo; require Exporter; @ISA = qw(Exporter); @EXPORT = qw(mysub); sub mysub ($) { print "mysub: @_\n" }; } BEGIN { warn("About to import\n"); Foo->import(); warn("Imported\n"); }
      I suspect that the warning comes when it imports and realizes that it has already parsed code whose meaning is being changed by the prototype. And the way I said that should go a long way to answering your question.

      BEGIN blocks are executed once the BEGIN block is parsed. That means that they run before later code is parsed, and after prior code is already parsed. This is also why BEGIN blocks run in the order they appear in the file...

        Strange, I only see this warning in Win32 AS Perl 5.6; it's not present under Linux 5.6.1/5.00503 or even Cygwin 5.6. With your variation, the warning comes out afterwards, so it looks as if the first line is the problem:
        About to import Imported main::mysub() called too early to check prototype at C:\Projects\GPerl +\Test\g1.pl line 1. mysub: 1
           MeowChow                                   
                       s aamecha.s a..a\u$&owag.print

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