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lang-bash
[[ $a =~ a|b ]]works with|being interpreted as OR in regex. In the approach of using a variable, the same regex is assigned to the variableregexp='a|b'. So the example doesn't seem to show that the variable approach avoids problems with quoting characters. However, the variable approach does make a difference when=~for regex is replaced with=for globbing.[[ $a = a|b ]]results insyntax error in conditional expression: unexpected token '|', whileregexp='a|b'; [[ $a = $regexp ]]doesn't. Why is the difference? Does parameter expansion ofregexpdelaya|b's appearing in the conditional expression, so that the delay can avoid some interpretation step which reports error on[[ $a = a|b ]]? What interpretation step is that?$regexp should *not* be quoted.line is worth its weight in gold. Thanks!