Parser fails on replacement tokens proxy_redirect ~^(http://[^:]+):\d+(/.+)$ $1$2;

[mg1213]

user root; http { server { proxy_redirect ~^(http://[^:]+):\d+(/.+)$ $1$2;
} }

[CodingFabian]

We have a case where the parser fails on this statement which extracts env variables from host headers:

        server_name ~^(?<subdomain>.+)\.example\.com$;

looks likely to be related