Gentoo – searching mail with notmuch

When setting up notmuch for use with mutt in Debian, I followed this guide
The macro setup there, didn’t work in the Gentoo installation, though.
I looked here and used the macro there:
macro index "unset wait_key\
read -p 'notmuch query: ' x; echo \$x >~/.cache/mutt_terms\ ~i \"\`notmuch search --output=messages \$(cat ~/.cache/mutt_terms)\
| head -n 600 | perl -le '@a=<>;chomp@a;s/\^id:// for@a;$,=\"|\";print@a'\`\"" \
"show only messages matching a notmuch pattern"