* Support ksh versions
Korn shell had two major versions: ’88 and ’93. Some systems have
ksh installed under the name `ksh93`. A few systems (maybe only
Solaris now) also have a `ksh88`. A few others use the `pdksh` (’88)
or `mksh` (’93) implementations, originated before ksh was open source.
Limit to currently-used versions
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Co-authored-by: Kevin Schoedel <kps@datatravelandexperiments.com>
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