in reply to @INC not reflecting correctly

I want the @INC to be as follows...

I would firstly create the following My_INC.pm: 
package My_INC;

BEGIN {
 @INC = qw(
/ajperznes/perl/localperl
/ajperznes/perl/lib/5.32.0/x86_64-linux
/ajperznes/perl/lib/5.32.0
/ajperznes/perl/lib/site_perl/5.32.0/x86_64-linux
/ajperznes/perl/lib/site_perl/5.32.0
/ajperznes/perl/lib/5.32.0/x86_64-linux
/ajperznes/perl/lib/5.32.0
          );
};

1;

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and place it in one of the existing @INC directories directories currently listed in @INC. (Create such a directory if none currently exist.)

Then set the PERL5OPT environment variable to -MMy_INC
Then, every time perl is invoked, @INC is set as desired.

On my Windows 7 machine: 
C:\>perl -le "print 'PERL5OPT: ' . $ENV{PERL5OPT}; print for @INC;"
PERL5OPT:
C:/perl-5.34.0/site/lib/MSWin32-x64-multi-thread
C:/perl-5.34.0/site/lib
C:/perl-5.34.0/lib/MSWin32-x64-multi-thread
C:/perl-5.34.0/lib

C:\>set PERL5OPT=-MMy_INC

C:\>perl -le "print 'PERL5OPT: ' . $ENV{PERL5OPT}; print for @INC;"
PERL5OPT: -MMy_INC
/ajperznes/perl/localperl
/ajperznes/perl/lib/5.32.0/x86_64-linux
/ajperznes/perl/lib/5.32.0
/ajperznes/perl/lib/site_perl/5.32.0/x86_64-linux
/ajperznes/perl/lib/site_perl/5.32.0
/ajperznes/perl/lib/5.32.0/x86_64-linux
/ajperznes/perl/lib/5.32.0

C:\>

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Cheers,
Rob

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Re^2: @INC not reflecting correctly
by syphilis (Archbishop) on Aug 27, 2021 at 03:44 UTC
    Then, every time perl is invoked, @INC is set as desired.

    Actually, that's not quite always so. This was not what I expected: 
    C:\>perl -MMath::BigInt -le "print 'PERL5OPT: ' . $ENV{PERL5OPT};print
+ for @INC;
"
PERL5OPT: -MMy_INC
/ajperznes/perl/localperl
/ajperznes/perl/lib/5.32.0/x86_64-linux
/ajperznes/perl/lib/5.32.0
/ajperznes/perl/lib/site_perl/5.32.0/x86_64-linux
/ajperznes/perl/lib/site_perl/5.32.0
/ajperznes/perl/lib/5.32.0/x86_64-linux
/ajperznes/perl/lib/5.32.0

    [download]
    I expected that command to fail because Math::BigInt does not exist in any of those @INC directories that are listed. (It exists only in one of my original @INC directories.)
    I expected that command to do the same as the following one-liner (in which PERL5OPT is unset): 
    C:\>perl -MMy_INC -MMath::BigInt -le "print 'PERL5OPT: ' . $ENV{PERL5O
+PT};print for @INC;"
Can't locate Math/BigInt.pm in @INC (you may need to install the Math:
+:BigInt module) (@INC contains: /ajperznes/perl/localperl /ajperznes/
+perl/lib/5.32.0/x86_64-linux /ajperznes/perl/lib/5.32.0 /ajperznes/pe
+rl/lib/site_perl/5.32.0/x86_64-linux /ajperznes/perl/lib/site_perl/5.
+32.0 /ajperznes/perl/lib/5.32.0/x86_64-linux /ajperznes/perl/lib/5.32
+.0).
BEGIN failed--compilation aborted.

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    But instead it processed the -MMath::BigInt before it processed the -MMy_INC. That is, it does the same as: 
    C:\>perl -MMath::BigInt -MMy_INC -le "print 'PERL5OPT: ' . $ENV{PERL5O
+PT};print
for @INC;"
PERL5OPT:
/ajperznes/perl/localperl
/ajperznes/perl/lib/5.32.0/x86_64-linux
/ajperznes/perl/lib/5.32.0
/ajperznes/perl/lib/site_perl/5.32.0/x86_64-linux
/ajperznes/perl/lib/site_perl/5.32.0
/ajperznes/perl/lib/5.32.0/x86_64-linux
/ajperznes/perl/lib/5.32.0

    [download]
    Is it possible to have perl process the contents of PERL5OPT *before* any -M... command line switches are processed ?

    UPDATE: I don't think this would be an issue for dirtdog because, IIUC, the directories in his original @INC don't exist anyway.

    Cheers,
    Rob
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      I'm pretty sure this is something that the Strawberry Perl Portable editions work around. I seem to remember there is some modification of Config.pm or one of its associated files to use local values. I just can't find the mechanism at the moment.

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        I'm pretty sure this is something that the Strawberry Perl Portable editions work around

        As regards @INC on Windows, there's no need to work around anything as wrt the setting of @INC.
        For example, I have a build of perl-5.30.0 in the location C:/_64/perl530_810.
        It reports @INC as being: 
            C:/_64/perl530_810/site/lib
    C:/_64/perl530_810/lib

        [download]
        I copy that perl to a new location of C:/_64/C/perl530_810.
        Without any need for me to take any additional action at all, this new perl installation correctly reports @INC as being: 
            C:/_64/C/perl530_810/site/lib
    C:/_64/C/perl530_810/lib

        [download]
        This is something that happens automatically on Windows. (I think it just looks at the location of the perl executable and derives @INC accordingly.)
        However, Linux (amazingly) apparently does not provide such a convenience.

        It's not quite so simple for portable Strawberry Perl wrt the correct treatment of %Config settings.
        I think they're probably just rewriting Config.pm and Config_heavy.pl at time of installation.
        (Again, this is a convenience that is unavailable to Linux.)

        Cheers,
        Rob
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