Im not sure if it issue with this plugin but when trying to use with 'babel-loader' line below :

loader : [
  { test: /myPattern/ , loader: 'babel-loader' }, 
  { test: /mySecondPattern/, loader: StringReplacePlugin({ settings }) },
] 

I see :
Element from loaders list should have one of the fields 'loader' or 'loaders'