The unset builtin treats attempts to unset array
                     subscripts @ and * differently depending on whether
                     the array is indexed or associative, and differently
                     than in previous versions.
              •      Arithmetic commands ( ((...)) ) and the expressions
                     in an arithmetic for statement can be expanded more
                     than once.
              •      Expressions used as arguments to arithmetic
                     operators in the [[ conditional command can be
                     expanded more than once.
              •      The expressions in substring parameter brace
                     expansion can be expanded more than once.
              •      The expressions in the $((...)) word expansion can
                     be expanded more than once.
              •      Arithmetic expressions used as indexed array
                     subscripts can be expanded more than once.
              •      test -v, when given an argument of A[@], where A is
                     an existing associative array, will return true if
                     the array has any set elements.  Bash-5.2 will look
                     for and report on a key named @.
              •      The ${parameter[:]=value} word expansion will return
                     value, before any variable-specific transformations
                     have been performed (e.g., converting to lowercase).
                     Bash-5.2 will return the final value assigned to the
                     variable.
              •      Parsing command substitutions will behave as if
                     extended globbing (see the description of the shopt
                     builtin above) is enabled, so that parsing a command
                     substitution containing an extglob pattern (say, as
                     part of a shell function) will not fail.  This
                     assumes the intent is to enable extglob before the
                     command is executed and word expansions are
                     performed.  It will fail at word expansion time if
                     extglob hasn't been enabled by the time the command
                     is executed.```