For example

*node_modules/foo/package.json*
~~~
"bin": {
   "not-my-pkg-name": "./bin/script.js",
   "not-my-pkg-name-2": "./bin/script2.js"
}
~~~

Proposal:
~~~
npm debug <package> --bin <name>
~~~
as a general syntax.

1. GIVEN there are multiple executables THEN there MUST be a `--bin` key and value in `argv`
2. GIVEN there's only a single `bin` object property THEN a `--bin` in `argv` *MAY* be omitted
3. GIVEN there is a `--bin` in `argv` THEN `<name>` MUST match some name in the `bin` object ELSE EXIT with NPM ERR.

So the example above requires
~~~
npm debug foo --bin not-my-pkg-name
~~~

However

*node_modules/foo/package.json*
~~~
"bin": {
   "not-my-pkg-name": "./bin/script.js"
}
~~~

or

~~~
{
  "bin": "./bin/script.js"
}
~~~

both allow for

~~~
npm debug foo
~~~

…debug both?

Allow for selecting which one to debug with --bin and --main argument.
When both arguments are given --bin takes precedence over --main.
When none are given fallback priority is the same.