`man zshzle` at the "zle widget" section:
A non-zero return status causes the shell to beep when the widget exits,
unless the BEEP options was unset or the widget was called via the zle
command. Thus if a user defined widget requires an immediate beep, it
should call the beep widget directly.
https://github.com/robbyrussell/oh-my-zsh/pull/215#issuecomment-1328406
To activate this script, load it into an interactive ZSH session:
% source history-substring-search.zsh
See the "history-substring-search.zsh" file for more information:
% sed -n '2,/^$/s/^#//p' history-substring-search.zsh | more