-[ -z "$BASH_COMPLETION" -a -r /etc/bash_completion ] \
- && source /etc/bash_completion
-[ -z "$BASH_COMPLETION" -a -r /usr/local/etc/bash_completion ] \
- && source /usr/local/etc/bash_completion
-[ -z "$BASH_COMPLETION" -a -r /opt/homebrew/etc/bash_completion ] \
- && source /opt/homebrew/etc/bash_completion
-[ -z "$BASH_COMPLETION" -a -r /opt/local/etc/bash_completion ] \
- && source /opt/local/etc/bash_completion
+if ! shopt -oq posix; then
+ [ -z "$BASH_COMPLETION" -a -r /etc/bash_completion ] \
+ && source /etc/bash_completion
+ [ -z "$BASH_COMPLETION" -a -r /usr/local/etc/bash_completion ] \
+ && source /usr/local/etc/bash_completion
+ [ -z "$BASH_COMPLETION" -a -r /opt/homebrew/etc/bash_completion ] \
+ && source /opt/homebrew/etc/bash_completion
+ [ -z "$BASH_COMPLETION" -a -r /opt/local/etc/bash_completion ] \
+ && source /opt/local/etc/bash_completion
+fi