the parser doesn't support 'pattern' constructs in the command you tried.

[realyukii]

while entering:

case "${BASH_SOURCE:-$0}" in
  */*) dir=${1%/*}; [ -z $dir ] && echo "/" || echo $dir ;;
  *) echo "." ;;
esac

it outputs:
the parser doesn't support 'pattern' constructs in the command you tried.

So, as the output says, I report it.

thank you