Create an event / plugin for Composer

I developed a portable WebServer and I'm creating a portable console too, to use Composer.

I have a problem. I need to create a plugin to add additional behavior to Composer.

I need that when downloading any package with Composer, it edits the composer.json "scripts" of that package, so that it works on the portable console.

When downloading Laravel, for example:

Original composer.json:

{
    "name": "laravel/laravel",
    ...
    "scripts": {
        "post-root-package-install": [
            "php -r \"file_exists('.env') || copy('.env.example', '.env');\""
        ],
        ...
    },
    ...
}

composer.json edited by the plugin:

{
    "name": "laravel/laravel",
    ...
    "scripts": {
        "post-root-package-install": [
            "F:/portable_php_path/php.exe -r \"file_exists('.env') || copy('.env.example', '.env');\""
        ],
        ...
    },
    ...
}

• Note that a physical path has been generated for php.exe, because in the portable version it can be in any path.

(My question is for the creation of the composer plugin. I have no problem editing the composer.json with PHP.)

I read the tutorial for creating a plugin on the composer site, but I was confused. (https://getcomposer.org/doc/articles/plugins.md)

If there is another way to do that, it's also interesting. I accept other suggestions and ideas.

Thanks to anyone who can help.

[Sorry my bad english]