> nix run nixpkgs.nodePackages.webpack nixpkgs.nodePackages.npm
$ webpack
$ webpack 
The CLI moved into a separate package: webpack-cli
Would you like to install webpack-cli? (That will run npm install -D webpack-cli) (yes/NO)yes
npm WARN awesome-typescript-loader@5.1.1 requires a peer of typescript@^2.7 but none is installed. You must install peer dependencies yourself.
npm WARN webpack-cli@3.0.8 requires a peer of webpack@^4.x.x but none is installed. You must install peer dependencies yourself.
npm WARN react-nodes@0.0.1 No repository field.

+ webpack-cli@3.0.8
added 76 packages from 32 contributors in 9.471s
[+] no known vulnerabilities found [1180 packages audited]

{ Error: Cannot find module 'webpack-cli'
    at Function.Module._resolveFilename (module.js:476:15)
    at Function.Module._load (module.js:424:25)
    at Module.require (module.js:504:17)
    at require (internal/module.js:20:19)
    at runCommand.then.result (/nix/store/x96639940sdbv2cpky54pf4xby51jvnl-node-webpack-4.8.3/lib/node_modules/webpack/bin/webpack.js:62:14)
    at process._tickCallback (internal/process/next_tick.js:109:7) code: 'MODULE_NOT_FOUND' }