<!-- check if this problem is already solved! github.com/issues?q=is:issue+user:fish-shell -->
- [ ] Have you checked if problem occurs with [fish 2.3.1](/fish-shell/fish-shell/releases/tag/2.3.1)?
- [ ] Tried fish without third-party customizations *(check `sh -c 'env HOME=$(mktemp -d) fish'`)*?

**fish version installed** *(`fish --version`)*:

**OS/terminal used**: 

Talk about the the issue here. 

## Reproduction steps
1. step one
2. …

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## Results
```console
~ $ math 2 + 2
5
```