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in reply to Using Look-ahead and Look-behind

Referring to the paragraph "Matching a pattern that doesn't include another pattern", I wonder why ?: is necessary. It seems to be working for me even without ?:. Please explain. thanks.

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Re^2: Using Look-ahead and Look-behind
by Roy Johnson (Monsignor) on Nov 12, 2007 at 17:54 UTC
    Generally, the decision about using ?: is not about whether it's necessary, but that capturing whatever you're grouping isn't necessary. The ?: modifier makes parentheses not capture, which is somewhat more efficient and might make the task of counting left parentheses less onerous.

    By the way, it's not a lookaround feature.

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