You can set the directories to be added to @INC by default when you compile Perl. Or more precisely: when you run Configure, before compiling.

So yes, the default is usually part of the binary distribution for a platform.

C:\dev\perls>dir 5.6.2
 Volume in drive C has no label.
 Volume Serial Number is 44B0-3C2E

 Directory of C:\dev\perls\5.6.2

07/27/2004  06:30 AM    <DIR>          .
07/27/2004  06:30 AM    <DIR>          ..
07/27/2004  07:31 AM    <DIR>          bin
07/27/2004  06:30 AM    <DIR>          html
07/27/2004  06:50 AM    <DIR>          lib
07/27/2004  06:29 AM    <DIR>          site
               0 File(s)              0 bytes
               6 Dir(s)  34,454,638,592 bytes free

C:\dev\perls>5.6.2\bin\perl -le"print for @INC"
C:/dev/perls/5.6.2/lib
.

C:\dev\perls>rename 5.6.2 v5.6.2

C:\dev\perls>v5.6.2\bin\perl -le"print for @INC"
C:/dev/perls/v5.6.2/lib
C:/dev/perls/v5.6.2/site/lib
.

C:\dev\perls>
C:\dev\perls>rename v5.6.2 5.6.2f

C:\dev\perls>5.6.2f\bin\perl -le"print for @INC"
C:/dev/perls/5.6.2f/lib
.

C:\dev\perls>rename 5.6.2f f

C:\dev\perls>f\bin\perl -le"print for @INC"
C:/dev/perls/f/lib
C:/dev/perls/f/site/lib
.

C:\dev\perls>f\bin\perl -V

Summary of my perl5 (revision 5 version 6 subversion 2) configuration:
  Platform:
    osname=MSWin32, osvers=4.0, archname=MSWin32-x86-multi-thread
    uname=''
    config_args='undef'
    hint=recommended, useposix=true, d_sigaction=undef
    usethreads=undef use5005threads=undef useithreads=define usemultip
+licity=define
    useperlio=undef d_sfio=undef uselargefiles=undef usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
  Compiler:
    cc='cl', ccflags ='-nologo -O1 -MD -DNDEBUG -DWIN32 -D_CONSOLE -DN
+O_STRICT -DHAVE_DES_FCRYPT  -DPERL_IMPLICIT_CONTEXT
-DPERL_IMPLICIT_SYS -DPERL_MSVCRT_READFIX',
    optimize='-O1 -MD -DNDEBUG',
    cppflags='-DWIN32'
    ccversion='', gccversion='', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=10
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
+ lseeksize=4
    alignbytes=8, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='link', ldflags ='-nologo -nodefaultlib -release  -libpath:"c:\
+dev\perls\f\lib\CORE"  -machine:x86'
    libpth=C:\PROGRA~1\MIAF9D~1\VC98\lib
    libs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib
+  comdlg32.lib advapi32.lib shell32.lib ole32.lib ol
eaut32.lib  netapi32.lib uuid.lib wsock32.lib mpr.lib winmm.lib  versi
+on.lib odbc32.lib odbccp32.lib msvcrt.lib
    perllibs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool
+.lib  comdlg32.lib advapi32.lib shell32.lib ole32.li
b oleaut32.lib  netapi32.lib uuid.lib wsock32.lib mpr.lib winmm.lib  v
+ersion.lib odbc32.lib odbccp32.lib msvcrt.lib
    libc=msvcrt.lib, so=dll, useshrplib=yes, libperl=perl56.lib
  Dynamic Linking:
    dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -release  -l
+ibpath:"c:\dev\perls\f\lib\CORE"  -machine:x86'



Characteristics of this binary (from libperl):
  Compile-time options: MULTIPLICITY USE_ITHREADS PERL_IMPLICIT_CONTEX
+T PERL_IMPLICIT_SYS
  Built under MSWin32
  Compiled at Jul 27 2004 07:58:39
  @INC:
    C:/dev/perls/f/lib
    C:/dev/perls/f/site/lib
    .
[download]

During the configuration process in preparation to build a new release of perl on your system, there are a number of questions and settings that refer to the location of libraries. Essentially, these paths are "Compiled In"; however, you can always change the default during the build.

A nifty build trick is to add library paths to be added to the front of the @INC path, thus overriding the built-ins with your own modules, should you choose to do so.

The relevant portion of code is

sh Configure -Accflags='-DAPPLLIB_EXP=\"/other/lib/dir\"'
[download]

Improving the perl build system to allow relocation without requiring recompilation is certainly do-able and is on the P5P wish list. One way to implement this is to build all executables with dummy and very long paths stuffed into the executable, then write a utility to binary edit them when you move them. Sounds hacky, but in practice it works well and is better than the alternatives.

ActiveState's reloc_perl utility is an example of one way to do it.

Not quite. How would it find Config.pm without knowing the @INC?

The answer, as others have said, is that @INC is built in to the Perl binary, so you can't change it without recompiling the binary.

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

*sigh* Too true. I must have bonked myself on the head too many times.

Are some generated instead of being hardcoded? I orignally installed my ActiveState perl in R:\U, but recently moved it to R:\Utils (without reinstalling), and I get:

>perl -le "$,=', '; print @INC"
r:/Utils/perl/lib, r:/Utils/perl/site/lib, .
[download]

I did have to edit Config.pm for PPM to work in the new directory.