I found the clause "as English verbs go" in one of the answers on [ELL](https://ell.stackexchange.com/revisions/56295/2):

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> In *The Cambridge Grammar of the English Language* (p.113-4), this is called "motional *be*", and **it's very unusual as English verbs go**. In this meaning, be appears only in perfect constructions [...]
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It was later edited to say:

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> In *The Cambridge Grammar of the English Language* (p.113-4), this is called "motional *be*", and **it has a requirement that's very unusual**. In this meaning, *be* appears only in perfect constructions [...]
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I tried hard to understand the meaning of the "as English verbs go" clause but failed. Will anyone clear the meaning of this?