http://www.perlmonks.org?node_id=222368


in reply to Re: modify @INC
in thread modify @INC

lib will take a variable. You just have to initialize that in a BEGIN block beforehand. This is Perl - compilation and execution are freely nestable.

Makeshifts last the longest.

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Re: Re^2: modify @INC
by Anonymous Monk on Jan 16, 2003 at 23:46 UTC
    Would it be an option to do something like:

    $a="/my/module/path";
eval "use lib '$a'";
eval { use MyModule; }

    [download]
    I recall once using eval & use together to dynamically load specific modules when needed... This was before I knew about AUTOLOAD and SelfLoader and all...
[reply]
[d/l]
      No, that won't work. The use inside the eval BLOCK is compiled at compile time, but the string in eval EXPR is not. eval "use Foo"; is nothing but an obfuscated way to say require Foo; Foo->import;

      Neither case is a job for eval here. If you want variable paths at compile time, you do the following:

      my $libpath;
BEGIN { $libpath = "/foo/bar"; }
use lib $libpath;

      [download]
      If you want to load modules with dynamic @INC at runtime, you make use of the aforemention construct: 
      {
    local @INC = ("/foo/bar", @INC);
    require Foo;
    Foo->import;
}

      [download]
      eval will not help. And $a is a really awful name for a variable (plus $a and $b are reserved for sort). :)

      Makeshifts last the longest.

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[d/l]
[select]
Re: Re^2: modify @INC
by mt2k (Hermit) on Dec 26, 2002 at 17:40 UTC
    Mmm... I just ran a test script and got a working version, but I can't get it to not display warning messages.

    BEGIN {
  my $a = "c:/";
  use lib "$a";
}

use GetWords;
print new GetWords;

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    The warning message (without -w swicth or 'use warnings'):

    Empty compile time value given to use lib at C:\Documents and Settings\mt2k\De sktop\testing.pl line 3 

    -------------------------------------
eval reverse@{[lreP
=>q{ tsuJ\{qq},' rehtonA'
,q{\}rekcaH },' tnirp']}[1+1+
1,1-1,1+1,1*1,(1+1)*(1+1)];
-------------------------------------
[reply]
[d/l]
      Mm? 
      my $somewhere;
BEGIN { $somewhere = q(/over/the/rainbow) }

use lib $somewhere;

      [download]

      Makeshifts last the longest.

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[d/l]

      Oh yeah.. that's funny. Get this - right as soon as the implicit BEGIN (via the use) is parsed inside the currently-being-parsed BEGIN block it is executed. So you're attempting to use $a in your nested BEGIN block prior to defining it. See?

       BEGIN {
   my $a = "c:/";
   BEGIN { require "$a"; import "$a"; }
 }

      [download]

      Fun Fun Fun in the Fluffy Chair

[reply]
[d/l]

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