• In POSIX sh, something is undefined.
• $'c-style-escapes'
• Testing Equality
• $"msgid"
• ${var:1} (substring expansion)
• Arithmetic for loops
• Arithmetic exponentiation
• standalone ((..))
• select loops
• Here-strings
• echo flags
• ${var/pat/replacement}
• printf %q
• jobs flags
• Redirect both stdout and stderr
• Prefixing signal names with SIG
• disown
• Errors with changed codes
• Exception