Bash - how to do string split

STR=A.B.C && STR2=${STR%.*} && echo ${STR2%.*} && echo ${STR2#*.} && STR4=${STR#*.} && echo ${STR4#*.}

DELIMITER='.' && STR=A.B.C && echo ${STR%${DELIMITER}*}

for i in $(echo A.B.C | sed -e 's/\./ /g'); do echo $i; done