# malformed regex
[[ a =~ * ]]; echo 1:ERR2:$?

[[ a/b =~ a.b ]]; echo 2:YES:$?
[[ a/b =~ /*b ]]; echo 3:YES:$?

v='[]b.-]'
[[ a/.b] =~ $v ]]; echo 4:YES:$?

v=']b.-'
[[ a/.b] =~ $v ]]; echo 5:no:$?
[[ a/.b] =~ [$v] ]]; echo 6:YES:$?