Command Line, Modify Var and the "=" Character

https://github.com/less/less.js/blob/2d43c0b9648daee7f226f1be9952654c80dea033/bin/lessc#L73-L76

To me, the above lines optimistically consider that no string variables containing an "=" char will ever be passed.
Considering the scenario where:

• in a less file, I define a selector variable:

@shell_selector: "html";
@shell: (~"@{shell_selector}");

@{shell}{
    /* ... */
}

• and in a command line:

lessc --modify-var="shell_selector='html[theme=dark]'" src/less/styles.less dist/css/styles-dark.css

The latter fails. The error message includes the line that cannot be interpreted by the parser:
@shell_selector: 'html[theme;
which is the result of the referenced lines of code on top.

Start at bin/lessc lines 73-76 and reproduce the issue with the provided --modify-var command and Less input. Trace how the command-line value is split, then verify that the selector value containing "=" reaches the parser intact without the shown error.