Capture variables from successful combination of sub-matches

Hi there (cross-post from re2),

Hopefully not a silly question, but is there a way to capture the variables of all possible matches and perform checks with them?

For example, if I use the following made-up SPIR-V:
```cpp
%end = OpVariable %_ptr_Function_int Function
%15 = OpLoad %int %n
%16 = OpLoad %int %n
OpStore %end %16
```
...the following checks will return `false`...
```cpp
const std::string check = R"(
CHECK: [[END:%\w+]] = OpVariable
CHECK: [[LOADED:%\w+]] = OpLoad %int %n
CHECK: OpStore [[END]] [[LOADED]]
)";
```
...despite `OpStore %end %16` being a possibility.

Is there a better syntactical way to capture all possible versions of what `LOADED` might be and return success if a match is found with one of these versions (instead of stopping after the first match)?