>> Starting from "emacs -Q -f -eshell", type "echo $exec-path " (note the 
>> trailing space), and then hit TAB. The result is this error:
>>
>>    pcomplete-match: Wrong type argument: stringp, ("/usr/bin" ...)
>>
>> This is a regression from Emacs 28, and it looks like it's due to 
>> 'pcomplete-here-using-help' assuming that all the pcomplete args are 
>> strings. However, 'exec-path' is a list (and Eshell reports it this way 
>> to pcomplete), so the completion fails. I think all that's necessary is 
>> checking that the pcomplete args are strings in 
>> 'pcomplete-here-using-help', but I know next to nothing about 
>> pcomplete...
>
> Adding Stefan, who should know more about pcomplete.
>
> Stefan, any suggestions?
>

I'm still not Stefan, but this bug is fixed by the attached patch.