NOTE: a similar package has been added to core which you probably want to use instead: import "core:text/match", see the docs here: pkg.odin-lang.org/core/text/match.
Package pattern is an implementation of the patterns syntax also found in Lua. They are a lot like regex but have some limitations and advantages. See the Lua documentation pages for in depth coverage and examples here: https://www.lua.org/pil/20.2.html.