You seem to have already figured out that [ABCD] is semi-equivalent to (A|B|C|D). What do you need help with?

It is more properly equivalent to (?:A|B|C|D). The difference is that (?: ... ) is strictly for grouping and alternation while ( ... ) also captures its contents into a variable that can be accessed with a number like $1, $2, $3, etc.

In reply to Re: regular expression-xerox by diotalevi
in thread regular expression-xerox by oz

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