read the glob docs! And never forget the sacrafice that glob is making for you.

extglob changes the way certain characters are parsed. It is necessary to have a newline (not just a semicolon) between shopt -s extglob and any subsequent commands to use it.You cannot enable extended globs inside a group command that uses them, because the entire block is parsed before the shopt is evaluated. Note that the typical function body is a group command. An unpleasant workaround could be to use a subshell command list as the function body.

Therefore, if you use this option in a script, it is best put right under the shebang line.

Toggle line numbers

   1 #!/usr/bin/env bash
   2 shopt -s extglob   # and others, such as nullglob dotglob
   3