how to use REGEX in queries like...

[arademaker]

% awk '$2 ~ /^[A-Z]\.$/' *.conllu

maybe something like ~= below?

% cat documents/*.conllu | udapy -q util.Eval node='if (node.form ~= "^[A-Z]\.$"): node.draw(attributes="form,lemma,upos,feats")

[martinpopel]

This is Python, so just use re.match("[A-Z]\.$", node.form) instead of (node.form ~= "^[A-Z]\.$"). Blocks util.Eval and util.Mark already include import re. Note that the initial ^ is not needed in re.match (unlike re.search).

BTW: util.Mark may be also useful here:

cat documents/*.conllu | udapy -qTMA util.Mark node='re.match("[A-Z]\.$", node.form)' | less -R