in reply to PERL5LIB different than 'use lib'

This is a quote from lib:
For each directory in LIST (called $dir here) the lib module also checks to see if a directory called $dir/$archname/auto exists. If so the $dir/$archname directory is assumed to be a corresponding architecture specific directory and is added to @INC in front of $dir.
If there is a subdirectory named "auto", then use lib seems to behave more like PERL5LIB in that it will also search in the architecture-dependent subdirectory for your module.

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Re^2: PERL5LIB different than 'use lib'
by almut (Canon) on May 07, 2009 at 03:01 UTC
    also checks to see if a directory called $dir/$archname/auto exists...

    Both PERL5LIB and use lib should behave the same in this respect. For example 

    $ mkdir -p testlib/x86_64-linux-gnu-thread-multi/auto

$ PERL5LIB=testlib perl -e'print join"\n",@INC'
testlib/x86_64-linux-gnu-thread-multi
testlib
/etc/perl
/usr/local/lib/perl/5.8.8
/usr/local/share/perl/5.8.8
/usr/lib/perl5
/usr/share/perl5
/usr/lib/perl/5.8
/usr/share/perl/5.8
/usr/local/lib/site_perl

$ perl -Mlib=testlib -e'print join"\n",@INC'
testlib/x86_64-linux-gnu-thread-multi
testlib
/etc/perl
/usr/local/lib/perl/5.8.8
/usr/local/share/perl/5.8.8
/usr/lib/perl5
/usr/share/perl5
/usr/lib/perl/5.8
/usr/share/perl/5.8
/usr/local/lib/site_perl

    [download]

    (the same applies to -Itestlib, btw)

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[select]
      You'd think they should, but they don't. Try the following: 
      $ PERL5LIB=/no/such/dir perl -le 'print for @INC' > foo
$ PERL5LIB= perl -le 'use lib "/no/such/dir"; print for @INC' > bar
$ diff -u foo bar--- foo 2009-05-07 16:24:12.000000000 -0700
+++ bar 2009-05-07 16:24:32.000000000 -0700
@@ -1,12 +1,3 @@
-/no/such/dir/5.8.6/x86_64-linux-thread-multi
-/no/such/dir/5.8.6
-/no/such/dir/x86_64-linux-thread-multi
-/no/such/dir/5.8.5
-/no/such/dir/5.8.4
-/no/such/dir/5.8.3
-/no/such/dir/5.8.2
-/no/such/dir/5.8.1
-/no/such/dir/5.8.0
 /no/such/dir
 /usr/lib64/perl5/5.8.6/x86_64-linux-thread-multi
 /usr/lib/perl5/5.8.6

      [download]
      And now we see the difference that saintmike was talking about. If you put stuff in $ENV{PERL5LIB}, it adds a list of internal hardcoded architecture specific directories to look in whether or not those directories exist, and regardless of the contents! By contrast use lib adds subdirectories based on a heuristic about their contents.
[reply]
[d/l]

        This seems to be some (compile-time) configuration option, as none of my perls exhibit that behavior. I've tried with various versions from 5.8.4 to 5.10.0, self-built and/or those that ship with Debian and SUSE Linux. All do produce identical results for PERL5LIB and use lib (both existing and non-existing dirs).

        As you're getting directories for all kinds of versions, I guess it's the configure option that's scanning for other installations of Perl... (which I never use, as I explicitly do want to keep my versions separate).

[reply]
[d/l]

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