Regex: Repeat pattern n times, with variation on final repetition

Question

I have a regular expression which is intended to match a specific syntax, n times, with a pipe (|) following each occurrence, except for the final occurrence. Currently, my pattern is along the lines of (pattern)\|{3}, but this doesn't satisfy the requirement that there is no trailing pipe. Is there anyway I can accomplish this without repeating (pattern)? The best solution I can think of is (pattern)\|{2}(pattern).

Valid Example:

*|401|[2-10]

Invalid Example:

*|401|[2-10]|

The value of (pattern) is extraneous to answering my specific question, but for completeness, here it is in its current form: (?:(?:((\*)|(\[[\w+ ]\-[\w+ ]\])|(\d+)))\|){3}

Edit

This is being consumed within .NET and JavaScript.

Answer 1

There is a simple solution, if you're matching the entire input string:

(?:pattern(?:\|(?!$)|$)){3}

Which means: match your pattern followed by:

• either \|(?!$): a pipe not followed by the end of the string
• or $ the end of the string

3 times.

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For your specific pattern, this would be:

^(?:(?:((\*)|(\[[\w+ ]\-[\w+ ]\])|(\d+)))(?:\|(?!$)|$)){3}

I also prefixed the pattern with ^, since this solution works only if you match the entire input anyway.