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Perl in a Nutshell, 2nd Edition
book

Perl in a Nutshell, 2nd Edition

by Nathan Patwardhan, Ellen Siever, Stephen Spainhour
June 2002
Beginner content levelBeginner
759 pages
80h 42m
English
O'Reilly Media, Inc.
Content preview from Perl in a Nutshell, 2nd Edition

Name

undef

Synopsis

undef expr
                  

Undefines the value of expr, which must be an lvalue. Use only on a scalar value, an entire array or hash, or a subroutine name (using the & prefix). Any storage associated with the object will be recovered for reuse (though not returned to the system, for most versions of Unix). The undef function will probably not do what you expect on most special variables. The function always returns the undefined value. This is useful because you can omit the expr, in which case nothing gets undefined, but you still get an undefined value that you could, for instance, return from a subroutine to indicate an error.

You may use undef as a placeholder on the left side of a list assignment, in which case the corresponding value from the right side is simply discarded. Apart from that, you may not use undef as an lvalue.

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Publisher Resources

ISBN: 0596002416Errata Page