Aginity puredata error with REGEXP_EXTRACT

Question

I have the following error when executing the REG_EXTRACT I do not know what the error will be.

You can also help me by indicating what this sentence is for, which I don't understand very well.

I run this on aginity puredata version 4.9.1.2686

Thanks for your help.

select REGEXP_EXTRACT('HELLO','(?<=EN_LA":")(.*?)"')

Error

ERROR [HY000] ERROR:  0 : Regex: pos(5) syntax error in subpattern name (missing terminator)
Culprit Pattern: (?<=EN_LA":")(.*?)"