Add an option in uglifyjs to enable excluding use of some variables when uglifying code

[anubmat]

Feature request

Is it possible to have an option that allows us to specify characters that we want the minifier to exclude from being used during minification. Something like excludeChars: ['$']
In my case, with minification, a function call is sometimes reduced to $(o), which is a macro for output path, and is thus misread by the interpreter.

Just to be clear, this is different from using the 'reserved' option, as I don't want '$' keyword from not being mangled, but I want the uglifier to not use $ when replacing variables/function_names

[vivekpan27]

The mangler option should help you with that https://github.com/mishoo/UglifyJS#cli-mangle-options