Pragmas having the same name like functions are a problem for doc, and there is no possible DWIM solution to decide which one is meant:

• https://perldoc.perl.org/functions/open.html
• https://perldoc.perl.org/open.html

Your attempt to write open.pm to indicate a module/pragma might be a workaround.

PS: FWIW personally I'm using my own JS solution, which takes the full URL but shortens the text.

• so this https://perldoc.perl.org/open.html#Implementation-Details
• becomes [HTTPs://perldoc.perl.org/open.html#Implementation-Details|open#Implementation-Details]
• displays open#Implementation-Details