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Perl provides three loop control keywords that all accept an optional loop label as an argument. If no label is specified, the keywords act on the innermost loop. Within nested loops, the use of labels enables control to move from an inner loop to an outer one, or out of the outer loop altogether.
The number of elements in an array can be determined either by evaluating the array in scalar context or with the help of the $# sigil. The latter gives the index of the last element in the array, not the number of elements. The expressions scalar(@array) and ($#array + 1) are equivalent.
The user can search for elements in an associative array, and delete elements from the array. The following shows how multi-dimensional associative arrays can be simulated in standard AWK using concatenation and the built-in string-separator variable SUBSEP:
Magic numbers become particularly confusing when the same number is used for different purposes in one section of code. It is easier to alter the value of the number, as it is not duplicated. Changing the value of a magic number is error-prone, because the same value is often used several times in different places within a program. [6]
But the initialization of the first_name and last_name members are incorrect. This is because if the length of first_name and last_name character arrays are less than 16 bytes, during the strcpy , [ 1 ] we fail to fully initialize the entire 16 bytes of memory reserved for each of these members.
Perl 5.6.1 and newer support autovivification of file and directory handles. [3] Calling open() on an undefined variable will set it to a filehandle. According to perl561delta, "[t]his largely eliminates the need for typeglobs when opening filehandles that must be passed around, as in the following example:
Dynamically typed languages usually treat undefined values explicitly when possible. For instance, Perl has undef operator [1] which can "assign" such value to a variable. In other type systems an undefined value can mean an unknown, unpredictable value, or merely a program failure on attempt of its evaluation.
The PDL API uses the basic Perl 5 object-oriented functionality: PDL defines a new type of Perl scalar object (eponymously called a "PDL", or "ndarray") that acts as a Perl scalar, but that contains a conventional typed array of numeric or character values. All of the standard Perl operators are overloaded so that they can be used on PDL ...