awk: fatal: Invalid regular expression when setting multiple field separators

Question

I was trying to solve Grep regex to select only 10 character using awk. The question consists in a string XXXXXX[YYYYY--ZZZZZ and the OP wants to p

Answer 1

This with GNU Awk 3.1.7

echo "XXXXXXX[YYYYY--ZZZZ" | awk -F"--|[[]" '{print $2}'    
echo "XXXXXXX[YYYYYbbZZZZ" | awk -F"bb|[[]" '{print $2}'