How to Pass Variables between Nested Includes in Gulp File Include?

I’m using gulp-file-include to build my HTML files and I’m running into an issue with passing variables between nested include files.

File Structure:

.
├── index.html
└── template-parts
    └── common
        ├── header.html
        └── headerMenuList.html

Problem:
I want to pass a variable (nav) from index.html to header.html and then pass it from header.html to headerMenuList.html. However, I’m getting the following error:

[21:14:05] Starting 'htmlConcat'...
[21:14:05] 'htmlConcat' errored after 11 ms
[21:14:05] Error in plugin "gulp-file-include"
Message:
    JSON5: invalid character 'a' at 1:11
Details:
    domainEmitter: [object Object]
    domainThrown: false

index.html:

<!-- siteHeader -->
@@include('template-parts/common/header.html', { "nav": "about" })

header.html:

<!-- I want to pass the nav variable to this file -->
<p>Navigation: @@nav</p>
<!-- Passing nav to headerMenuList.html -->
@@include('./headerMenuList.html', { "nav": nav })

headerMenuList.html:

<!-- Trying to access nav variable here -->
<p>Current Navigation: @@nav</p>

What I’ve Tried:
Direct Variable Passing: Using @@include('./headerMenuList.html', { "nav": nav }) but it throws the JSON5 error.
String Interpolation: Tried using <%= nav %> inside header.html but it outputs <%= nav %> as a string instead of the value.
Direct String Testing: When I change it to @@include('./headerMenuList.html', { "nav": "about" }), it works, indicating that the variable isn’t being passed correctly.
Question:
Is it possible to pass variables between nested include files in gulp-file-include? If so, what is the correct way to do this? If not, is there a workaround or alternative approach I can use to achieve this?

Thanks in advance for your help!