14.7.4 Notes

Filename expansion is performed on the right hand side of a parameter assignment, including those appearing after commands of the typeset family. In this case, the right hand side will be treated as a colon-separated list in the manner of the PATH parameter, so that a ‘~’ or an ‘=’ following a ‘:’ is eligible for expansion. All such behaviour can be disabled by quoting the ‘~’, the ‘=’, or the whole expression (but not simply the colon); the EQUALS option is also respected.

If the option MAGIC_EQUAL_SUBST is set, any unquoted shell argument in the form ‘identifier=expression’ becomes eligible for file expansion as described in the previous paragraph. Quoting the first ‘=’ also inhibits this.