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Perl Language Reference Manual
by Larry Wall and others
Paperback (6"x9"), 724 pages
ISBN 9781906966027
RRP £29.95 ($39.95)

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29.21 U

UDP
User Datagram Protocol, the typical way to send datagrams over the Internet.
UID
A user ID. Often used in the context of file or process ownership.
umask
A mask of those permission bits that should be forced off when creating files or directories, in order to establish a policy of whom you'll ordinarily deny access to. See the umask ( ) function.
unary operator
An operator with only one operand, like ! or chdir ( ). Unary operators are usually prefix operators; that is, they precede their operand. The ++ and -- operators can be either prefix or postfix. (Their position does change their meanings.)
Unicode
A character set comprising all the major character sets of the world, more or less. See "Unicode support in Perl" (perlunicode) in the Perl Unicode and Locales Manual and http://www.unicode.org.
Unix
A very large and constantly evolving language with several alternative and largely incompatible syntaxes, in which anyone can define anything any way they choose, and usually do. Speakers of this language think it's easy to learn because it's so easily twisted to one's own ends, but dialectical differences make tribal intercommunication nearly impossible, and travelers are often reduced to a pidgin-like subset of the language. To be universally understood, a Unix shell programmer must spend years of study in the art. Many have abandoned this discipline and now communicate via an Esperanto-like language called Perl. In ancient times, Unix was also used to refer to some code that a couple of people at Bell Labs wrote to make use of a PDP-7 computer that wasn't doing much of anything else at the time.
ISBN 9781906966027Perl Language Reference ManualSee the print edition