Specification for Catch (⎊)

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@@ -75,6 +75,8 @@ Inferred properties are specified in [their own document](inferred.md), not in t
 
 - **Assert** (`!`) causes an error if the argument is not `1`. If `𝕨` is provided, it gives a message to be associated with this error (which can be any value, not necessarily a string).
 
+- **Catch** (`⎊`) evaluates `𝔽` on the arguments `𝕨` (if present) and `𝕩`. If `𝔽` completes without error it returns the result, but if evaluation of `𝔽` results in an error then the error is suppressed, and Catch evaluates `𝔾` on the arguments and returns the result. Errors in `𝔾` are not caught. Catch only prevents evaluation errors, and not syntax errors: these are considered errors in the program as a whole rather than any particular part of it.
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 ## Commentary on other primitives
 
 As noted above, see [reference.bqn](reference.bqn) for the authoritative definitions. Commentary here gives an overall description and highlights implementation subtleties and edge cases.