slap's clipboard plugin
Installed by default since 0.1.0 (the first version that supported plugins). If you are writing your own plugin, you can modify the following install command to suit your needs:
$ git clone https://github.com/slap-editor/slap-clipboard-plugin.git ~/.slap/plugins/slap-clipboard-plugin
$ cd ~/.slap/plugins/slap-clipboard-plugin
$ npm install
Adds copy (C-c by default), cut (C-x), and paste (C-v) bindings. Also adds
Editor.prototype.copy and Editor.prototype.paste.
On Linux, xclip is required.