Common Expression Language (Rust) The Common Expression Language (CEL) is a non-Turing complete language designed for simplicity, speed, safety, and portability. CEL's C-like syntax looks nearly identical to equivalent expressions in C++, Go, Java, and TypeScript. CEL is ideal for lightweight expression evaluation when a fully sandboxed scripting language is too resource intensive. // Check whether a resource name starts with a group name. resource.name.startsWith("/groups/" + auth.claims.group)...