Re^2: use depending on environment

This is the "correct" way to do this as use is a compile-time directive (is that the right term?). Perl will see the use inside the BEGIN { } or the eval { } and go search for that module.

Addmittedly, it is seems odd that

BEGIN {
  if ($condition) {
    use Foo;
  }
}
[download]

does not do what you expect; but it makes more sense if you think of what it really does. Convert the above code into

BEGIN {
  if ($condition) {
    BEGIN {
      require Foo;
      Foo::import();
    }
  }
}
[download]

Then remember that if you have this:

print Bar::new();
print Bar::old();

package Bar;

sub new {
  sub old {
    return "I'm old";
  }
  return "I'm new";
}

1;
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you have created a real subroutine called "old" in package Bar that can be called. The same is true with the use inside the BEGIN { }; you created a real BEGIN { } block that will be executed at compile time in the order in which it was encountered. You will actually execute that code regardless of the if { } block that surrounds it.

Ivan Heffner
Sr. Software Engineer, DAS Lead
WhitePages.com, Inc.

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Re^3: use depending on environment by tlm (Prior) on Jun 22, 2005 at 17:18 UTC
Just a couple of things. According to the docs for `use`: [`use`] is exactly equivalent to `BEGIN { require Module; import Module LIST; }` [download] except that Module must be a bareword. In other words, at least according to the docs, if one wants to replicate at runtime what `use` does, it should be `Foo->import`, not `Foo::import`. The second point is only a clarification of a potentially misleading detail. The routine `Bar::old` in your example can be called even if `Bar::new` has not been called first. In other words, it is not the case that executing `Bar::new` somehow defines `Bar::old`. (I'm not saying that you wrote or believe this, but someone reading your post may incorrectly draw this conclusion.) the lowliest monk	[reply] [d/l]
Re^3: use depending on environment - ok by Andre_br (Pilgrim) on Jun 22, 2005 at 20:40 UTC
WOW! GOT IT! Sorry, but we in fact have written lots of VALID code. The REAL problem was that I was relying on a sub called from other script to do the `lc` work. And, I didn´t know, it didn´t get the locale set at the main script! But now it´s great. Sorry to make you guys hit heads too! But at least now we have a huge record of "use depending on envirnoment"! Cheers	[reply] [d/l]
Re^4: use depending on environment - ok by jhourcle (Prior) on Jun 22, 2005 at 23:23 UTC
For when there's someone months from now with the same problem, could you post what your final, working version was? (there were lots of versions that you've posted ... if you just want to go back and edit them, to mark which one did, and which ones didn't work, that'd be good, too... of course, it looked like they were all marked as not working)	[reply]
Re^3: use depending on environment by Andre_br (Pilgrim) on Jun 22, 2005 at 19:42 UTC
This one also doesn´t work... I am beggining to think about suicide! `BEGIN { ## ## use locale; ## ## eval "use POSIX ('locale_h')"; ## eval "setlocale( LC_ALL, 'pt_BR.iso88591' )"; ## ## } ##` [download] PS: no errors generated, just the incorrect default locale that remains set.	[reply] [d/l]
Re^3: use depending on environment by Andre_br (Pilgrim) on Jun 22, 2005 at 19:50 UTC
Sorry guys, this is getting a little bit confusing for me, I am not very familiar with this routines. I´m testing the code below without successs: `BEGIN { ## ## use locale; ## ## unless ( $ENV{REMOTE_ADDR} eq "127.0.0.1" ) { ## ## use POSIX ('locale_h'); ## setlocale( LC_ALL, "pt_BR.iso88591" ); ## ## } ## ## }` [download]	[reply] [d/l]
Re^4: use depending on environment by QM (Parson) on Jun 22, 2005 at 20:33 UTC
Have you read tlm's suggestion? -QM -- Quantum Mechanics: The dreams stuff is made of	[reply]