FAQ 6.21 What's wrong with using grep in a void context?

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6.21: What's wrong with using grep in a void context?

    The problem is that grep builds a return list, regardless of the
    context. This means you're making Perl go to the trouble of building a
    list that you then just throw away. If the list is large, you waste both
    time and space. If your intent is to iterate over the list, then use a
    for loop for this purpose.

    In perls older than 5.8.1, map suffers from this problem as well. But
    since 5.8.1, this has been fixed, and map is context aware - in void
    context, no lists are constructed.


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