gem:tldr:8b664

This is a command written in the Unix shell scripting syntax (specifically, the bash shell). Here's the breakdown of each component:

1. gem uninstall: This is the command to uninstall a Ruby gem. The gem command is used to interact with RubyGems, the package manager for Ruby.
2. ${gemname}: This is a placeholder for the name of the gem you want to uninstall. You should replace ${gemname} with the actual name of the gem you want to uninstall.
3. --version: This option allows you to specify a particular version of the gem to uninstall.
4. ${1-0-0}: Another placeholder, this time for the version number of the gem you want to uninstall. You should replace ${1-0-0} with the actual version number you want to uninstall.

For example, if you want to uninstall a gem called "example_gem" with version "1.0.0", you would replace ${gemname} with "example_gem" and ${1-0-0} with "1.0.0". The resulting command would be:

gem uninstall example_gem --version 1.0.0