Turning AI into a Developer Superpower: The PERL5LIB Auto-Setter

Like most developers, I have a mental folder labelled “useful little tools I’ll probably never build.” Small utilities, quality-of-life scripts, automations — they’d save time, but not enough to justify the overhead of building them. So they stay stuck…


This content originally appeared on DEV Community and was authored by Dave Cross

Like most developers, I have a mental folder labelled “useful little tools I’ll probably never build.” Small utilities, quality-of-life scripts, automations — they’d save time, but not enough to justify the overhead of building them. So they stay stuck in limbo.

That changed when I started using AI as a regular part of my development workflow.

Now, when I hit one of those recurring minor annoyances — something just frictiony enough to slow me down — I open a ChatGPT tab. Twenty minutes later, I usually have a working solution. Not always perfect, but almost always 90% of the way there. And once that initial burst of momentum is going, finishing it off is easy.

It’s not quite mind-reading. But it is like having a superpowered pair programmer on tap.

The Problem

Obviously, I do a lot of Perl development. When working on a Perl project, it’s common to have one or more lib/ directories in the repo that contain the project’s modules. To run test scripts or local tools, I often need to set the PERL5LIB environment variable so that Perl can find those modules.

But I’ve got a lot of Perl projects — often nested in folders like ~/git, and sometimes with extra lib/ directories for testing or shared code. And I switch between them frequently. Typing:

export PERL5LIB=lib

…over and over gets boring fast. And worse, if you forget to do it, your test script breaks with a misleading “Can’t locate Foo/Bar.pm” error.

What I wanted was this:

  • Every time I cd into a directory, if there are any valid lib/ subdirectories beneath it, set PERL5LIB automatically.

  • Only include lib/ dirs that actually contain .pm files.

  • Skip junk like .vscode, blib, and old release folders like MyModule-1.23/.

  • Don’t scan the entire world if I cd ~/git, which contains hundreds of repos.

  • Show me what it’s doing, and let me test it in dry-run mode.

The Solution

With ChatGPT, I built a drop-in Bash function in about half an hour that does exactly that. It’s now saved as perl5lib_auto.sh, and it:

  • Wraps cd() to trigger a scan after every directory change

  • Finds all qualifying lib/ directories beneath the current directory

  • Filters them using simple rules:

  • Excludes specific top-level directories (like ~/git) by default

  • Lets you configure everything via environment variables

  • Offers verbose, dry-run, and force modes

  • Can append to or overwrite your existing PERL5LIB

You drop it in your ~/.bashrc (or wherever you like), and your shell just becomes a little bit smarter.

Usage Example 

source ~/bin/perl5lib_auto.sh

cd ~/code/MyModule
# => PERL5LIB set to: /home/user/code/MyModule/lib

PERL5LIB_VERBOSE=1 cd ~/code/AnotherApp
# => [PERL5LIB] Found 2 eligible lib dir(s):
# => /home/user/code/AnotherApp/lib
# => /home/user/code/AnotherApp/t/lib
# => PERL5LIB set to: /home/user/code/AnotherApp/lib:/home/user/code/AnotherApp/t/lib

You can also set environment variables to customise behaviour:

export PERL5LIB_EXCLUDE_DIRS="$HOME/git:$HOME/legacy"
export PERL5LIB_EXCLUDE_PATTERNS=".vscode:blib"
export PERL5LIB_LIB_CAP=5
export PERL5LIB_APPEND=1

Or simulate what it would do:

PERL5LIB_DRYRUN=1 cd ~/code/BigProject

Try It Yourself

The full script is available on GitHub:

I’d love to hear how you use it — or how you’d improve it. Feel free to:

  • ⭐ Star the repo

  • 🐛 Open issues for suggestions or bugs

  • 🔀 Send pull requests with fixes, improvements, or completely new ideas

It’s a small tool, but it’s already saved me a surprising amount of friction. If you’re a Perl hacker who jumps between projects regularly, give it a try — and maybe give AI co-coding a try too while you’re at it.

What useful little utilities have you written with help from an AI pair-programmer?

The post Turning AI into a Developer Superpower: The PERL5LIB Auto-Setter first appeared on Perl Hacks.


This content originally appeared on DEV Community and was authored by Dave Cross


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Dave Cross | Sciencx (2025-05-14T16:22:11+00:00) Turning AI into a Developer Superpower: The PERL5LIB Auto-Setter. Retrieved from https://www.scien.cx/2025/05/14/turning-ai-into-a-developer-superpower-the-perl5lib-auto-setter/

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