|Perl Language Reference Manual|
by Larry Wall and others
Paperback (6"x9"), 724 pages
RRP £29.95 ($39.95)
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In list context, returns a list value consisting of the elements of LIST in the opposite order. In scalar context, concatenates the elements of LIST and returns a string value with all characters in the opposite order.
print join(", ", reverse "world", "Hello"); # Hello, world print scalar reverse "dlrow ,", "olleH"; # Hello, world
Used without arguments in scalar context, reverse() reverses
$_ = "dlrow ,olleH"; print reverse; # No output, list context print scalar reverse; # Hello, world
Note that reversing an array to itself (as in
@a = reverse @a) will
preserve non-existent elements whenever possible, i.e., for non magical
arrays or tied arrays with
This operator is also handy for inverting a hash, although there are some caveats. If a value is duplicated in the original hash, only one of those can be represented as a key in the inverted hash. Also, this has to unwind one hash and build a whole new one, which may take some time on a large hash, such as from a DBM file.
%by_name = reverse %by_address; # Invert the hash
|ISBN 9781906966027||Perl Language Reference Manual||See the print edition|