Mastering Modern Perl: Writing Efficient and Maintainable Code/

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Looping Directives: while and until

Looping Directives: while and until

Learn about the while and until looping directives.

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The while directive

A while loop continues until the loop conditional expression evaluates to a false value. Here’s an idiomatic infinite loop:

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while (1) { 
    # ...
}

Unlike the iteration foreach-style loop, the while loop’s condition has no side effects. If @values has one or more elements, this code is also an infinite loop, because every iteration will evaluate @values in scalar context to a non-zero value and iteration will continue:

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my @values = (0, 1, 2, 3, 4);
while (@values) {
    say $values[0];
}

To prevent such an infinite while loop, use a destructive update of the @values array by modifying the array ...