Perl: How to avoid adding current directory to module include path?

Question

I'd like to override some perl modules from a perl tool installed via conda. Perl is v5.26.2 installed via conda-forge. However, I cannot overwrite any scripts which are located in the same directory as $SCRIPT because perl always prepends the location of the script to the module directories:

/opt/anaconda/envs/vep-99/share/ensembl-vep-99.2-0/modules
/opt/anaconda/envs/vep-99/share/ensembl-vep-99.2-0
/home/user/.local/lib/perl5/lib/perl5/x86_64-linux-thread-multi
/home/user/.local/lib/perl5/lib/perl5
/opt/anaconda/envs/vep-99/lib/site_perl/5.26.2/x86_64-linux-thread-multi
/opt/anaconda/envs/vep-99/lib/site_perl/5.26.2
/opt/anaconda/envs/vep-99/lib/5.26.2/x86_64-linux-thread-multi
/opt/anaconda/envs/vep-99/lib/5.26.2
.

I now did a very ugly hack which simply changes the working directory for perl:

#!/bin/bash                                                                                                                                                                                                                                                                                                                                                                                 
                                                                                                                                                                                                                                                                                                                                                                                             
SCRIPT="${SCRIPT:-vep}"
SCRIPT_DIR="$(dirname $(realpath $(which $SCRIPT)))"
 
export PERL5LIB="$PERL5LIB:$SCRIPT_DIR:$SCRIPT_DIR/modules"

cd /
 
# fake script location to be in the current working directory
cat $(which $SCRIPT) | perl $@

This results in the following @INC:

//modules
/
/home/user/.local/lib/perl5/lib/perl5/x86_64-linux-thread-multi
/home/user/.local/lib/perl5/lib/perl5
/opt/anaconda/envs/vep-99/share/ensembl-vep-99.2-0
/opt/anaconda/envs/vep-99/share/ensembl-vep-99.2-0/modules
/opt/anaconda/envs/vep-99/lib/site_perl/5.26.2/x86_64-linux-thread-multi
/opt/anaconda/envs/vep-99/lib/site_perl/5.26.2
/opt/anaconda/envs/vep-99/lib/5.26.2/x86_64-linux-thread-multi
/opt/anaconda/envs/vep-99/lib/5.26.2
.

This technically works, but there is still /, //modules and . in the include path. Is there a way to get rid of that?

Answer 1

It's the following that's adding the first two directories:

export PERL5LIB="$PERL5LIB:$SCRIPT_DIR:$SCRIPT_DIR/modules"

Instead of adding cd /, just remove or comment out that line.

---

As for ., it's hardcoded up Perl 5.26 (released in 2017) and absent from then on. Removing it would require running something like the following:

# Remove relative paths from `@INC` (on unix systems).
BEGIN { @INC = grep m{^/}, @INC; }

But, since . is last in @INC, it doesn't hinder your attempts to override modules.