negation demo

bash-4.2$ range='1'; until [[ $range =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3} ]]; do echo "$range NOT OK"; range+='.2'; sleep 1; done
1 NOT OK
1.2 NOT OK
1.2.2 NOT OK

bash-4.2$ range='1'; while ! [[ $range =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3} ]]; do echo "$range NOT OK"; range+='.2'; sleep 1; done
1 NOT OK
1.2 NOT OK
1.2.2 NOT OK

bash-4.2$ range='1'; while [[ !( $range =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3} ) ]]; do echo "$range NOT OK"; range+='.2'; sleep 1; done
1 NOT OK
1.2 NOT OK
1.2.2 NOT OK
1.2.2.2 NOT OK
1.2.2.2.2 NOT OK
^C