ACM acmart template anonymous mode conditional text

I'm writing a conference paper using the acmart template. As the conference is blind, I've set the anonymous=true option (How to remove author information in sigconf template (acmart.cls) for double blind conferences?) and it works great! Not happy with that, I wondered how to print a block of text if I'm in anonymous mode?

I looked at the acmart.cls file and it defines a boolean key:

\define@boolkey+{acmart.cls}[@ACM@]{anonymous}[true]{%
\if@ACM@anonymous
\PackageInfo{\@classname}{Using anonymous mode}%
\else
\PackageInfo{\@classname}{Not using anonymous mode}%
\fi}


I tried to use this inside my document:

  \if@ACM@anonymous
\textbf{last line should be 901!}
\fi


It is a reminder not to go over 8 pages :-) , but the text is not displayed. How can I make this work?

@ has special meaning and can't be used as-is with macros. You need to brace your @-enabled commands using a \makeatletter-\makeatother pair:
\makeatletter