I don't see anything set for an environment variable named PERL5LIB:

$ echo $PERL5LIB

$
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Here is some more information:

$ perl -V
Summary of my perl5 (revision 5 version 10 subversion 1) configuration
+:
   
  Platform:
    osname=darwin, osvers=8.11.1, archname=darwin-2level
    uname='darwin cws-computer.local 8.11.1 darwin kernel version 8.11
+.1: wed oct 10 18:23:28 pdt 2007; root:xnu-792.25.20~1release_i386 i3
+86 i386 '
    config_args='-de'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=und
+ef
    use64bitint=undef, use64bitall=undef, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fno-common -DPERL_DARWIN -no-cpp-precomp -fno-
+strict-aliasing -pipe -I/usr/local/include',
    optimize='-O3',
    cppflags='-no-cpp-precomp -fno-common -DPERL_DARWIN -no-cpp-precom
+p -fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion='', gccversion='4.0.1 (Apple Computer, Inc. build 5370)'
+, gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=1
+6
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
+ lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='env MACOSX_DEPLOYMENT_TARGET=10.3 cc', ldflags =' -L/usr/local
+/lib'
    libpth=/usr/local/lib /usr/lib
    libs=-ldbm -ldl -lm -lc
    perllibs=-ldl -lm -lc
    libc=/usr/lib/libc.dylib, so=dylib, useshrplib=false, libperl=libp
+erl.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=bundle, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags=' -bundle -undefined dynamic_lookup -L/u
+sr/local/lib'


Characteristics of this binary (from libperl): 
  Compile-time options: PERL_DONT_CREATE_GVSV PERL_MALLOC_WRAP
                        USE_LARGE_FILES USE_PERLIO
  Built under darwin
  Compiled at Nov  5 2009 01:43:02
  @INC:
    /usr/local/lib/perl5/5.10.1/darwin-2level
    /usr/local/lib/perl5/5.10.1
    /usr/local/lib/perl5/site_perl/5.10.1/darwin-2level
    /usr/local/lib/perl5/site_perl/5.10.1
    /usr/local/lib/perl5/site_perl/5.8.6
    /usr/local/lib/perl5/site_perl
    .
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Can you explain this statement:

PERL5LIB=$PERL5LIB:/Library/Perl/5.8.6:/System/Library/Perl/5.8.6
export PERL5LIB
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Why would I want anything to point to my system's install of perl 5.8.6 when I want to use my own install of perl 5.10.1?

Thanks.