perlglossary.1

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A feature of \*(L"operator overloading\*(R" of objects, whereby
the behavior of certain operators can be reasonably
deduced using more fundamental operators.  This assumes that the
overloaded operators will often have the same relationships as the
regular operators.  See perlop.
.IP "autoincrement" 4
.IX Item "autoincrement"
To add one to something automatically, hence the name of the \f(CW\*(C`++\*(C'\fR
operator.  To instead subtract one from something automatically is
known as an \*(L"autodecrement\*(R".
.IP "autoload" 4
.IX Item "autoload"
To load on demand.  (Also called \*(L"lazy\*(R" loading.)  Specifically, to
call an \s-1AUTOLOAD\s0 subroutine on behalf of an
undefined subroutine.
.IP "autosplit" 4
.IX Item "autosplit"
To split a string automatically, as the \fB\-a\fR \*(L"switch\*(R" does when
running under \fB\-p\fR or \fB\-n\fR in order to emulate \*(L"awk\*(R".  (See also
the AutoSplit module, which has nothing to do with the \fB\-a\fR
switch, but a lot to do with autoloading.)
.IP "autovivification" 4
.IX Item "autovivification"
A Greco-Roman word meaning \*(L"to bring oneself to life\*(R".  In Perl,
storage locations (lvalues) spontaneously generate
themselves as needed, including the creation of any \*(L"hard reference\*(R"
values to point to the next level of storage.  The assignment
\&\f(CW\*(C`$a[5][5][5][5][5] = "quintet"\*(C'\fR potentially creates five scalar
storage locations, plus four references (in the first four scalar
locations) pointing to four new anonymous arrays (to hold the last
four scalar locations).  But the point of autovivification is that you
don't have to worry about it.
.IP "\s-1AV\s0" 4
.IX Item "AV"
Short for \*(L"array value\*(R", which refers to one of Perl's internal data
types that holds an \*(L"array\*(R".  The \*(L"\s-1AV\s0\*(R" type is a subclass of
\&\*(L"\s-1SV\s0\*(R".
.IP "awk" 4
.IX Item "awk"
Descriptive editing term\*(--short for \*(L"awkward\*(R".  Also coincidentally
refers to a venerable text-processing language from which Perl derived
some of its high-level ideas.
.Sh "B"
.IX Subsection "B"
.IP "backreference" 4
.IX Item "backreference"
A substring captured by a subpattern within
unadorned parentheses in a \*(L"regex\*(R".  Backslashed decimal numbers
(\f(CW\*(C`\e1\*(C'\fR, \f(CW\*(C`\e2\*(C'\fR, etc.)  later in the same pattern refer back to the
corresponding subpattern in the current match.  Outside the pattern,
the numbered variables (\f(CW$1\fR, \f(CW$2\fR, etc.) continue to refer to these
same values, as long as the pattern was the last successful match of
the current dynamic scope.
.IP "backtracking" 4
.IX Item "backtracking"
The practice of saying, \*(L"If I had to do it all over, I'd do it
differently,\*(R" and then actually going back and doing it all over
differently.  Mathematically speaking, it's returning from an
unsuccessful recursion on a tree of possibilities.  Perl backtracks
when it attempts to match patterns with a \*(L"regular expression\*(R", and
its earlier attempts don't pan out.  See \*(L"Backtracking\*(R" in perlre.
.IP "backward compatibility" 4
.IX Item "backward compatibility"
Means you can still run your old program because we didn't break any
of the features or bugs it was relying on.
.IP "bareword" 4
.IX Item "bareword"
A word sufficiently ambiguous to be deemed illegal under use strict
\&'subs'.  In the absence of that stricture, a
bareword is treated as if quotes were around it.
.IP "base class" 4
.IX Item "base class"
A generic \*(L"object\*(R" type; that is, a \*(L"class\*(R" from which other, more
specific classes are derived genetically by \*(L"inheritance\*(R".  Also
called a \*(L"superclass\*(R" by people who respect their ancestors.
.IP "big-endian" 4
.IX Item "big-endian"
From Swift: someone who eats eggs big end first.  Also used of
computers that store the most significant \*(L"byte\*(R" of a word at a
lower byte address than the least significant byte.  Often considered
superior to little-endian machines.  See also \*(L"little-endian\*(R".
.IP "binary" 4
.IX Item "binary"
Having to do with numbers represented in base 2.  That means there's
basically two numbers, 0 and 1.  Also used to describe a \*(L"non-text
file\*(R", presumably because such a file makes full use of all the binary
bits in its bytes.  With the advent of \*(L"Unicode\*(R", this distinction,
already suspect, loses even more of its meaning.
.IP "binary operator" 4
.IX Item "binary operator"
An \*(L"operator\*(R" that takes two operands.
.IP "bind" 4
.IX Item "bind"
To assign a specific \*(L"network address\*(R" to a \*(L"socket\*(R".
.IP "bit" 4
.IX Item "bit"
An integer in the range from 0 to 1, inclusive.  The smallest possible
unit of information storage.  An eighth of a \*(L"byte\*(R" or of a dollar.
(The term \*(L"Pieces of Eight\*(R" comes from being able to split the old
Spanish dollar into 8 bits, each of which still counted for money.
That's why a 25\-cent piece today is still \*(L"two bits\*(R".)
.IP "bit shift" 4
.IX Item "bit shift"
The movement of bits left or right in a computer word, which has the
effect of multiplying or dividing by a power of 2.
.IP "bit string" 4
.IX Item "bit string"
A sequence of bits that is actually being thought of as a
sequence of bits, for once.
.IP "bless" 4
.IX Item "bless"
In corporate life, to grant official approval to a thing, as in, \*(L"The
\&\s-1VP\s0 of Engineering has blessed our WebCruncher project.\*(R" Similarly in
Perl, to grant official approval to a \*(L"referent\*(R" so that it can
function as an \*(L"object\*(R", such as a WebCruncher object.  See
\&\*(L"bless\*(R" in perlfunc.
.IP "block" 4
.IX Item "block"
What a \*(L"process\*(R" does when it has to wait for something: \*(L"My process
blocked waiting for the disk.\*(R"  As an unrelated noun, it refers to a
large chunk of data, of a size that the \*(L"operating system\*(R" likes to
deal with (normally a power of two such as 512 or 8192).  Typically
refers to a chunk of data that's coming from or going to a disk file.
.IP "\s-1BLOCK\s0" 4
.IX Item "BLOCK"
A syntactic construct consisting of a sequence of Perl
statements that is delimited by braces.  The \f(CW\*(C`if\*(C'\fR and
\&\f(CW\*(C`while\*(C'\fR statements are defined in terms of BLOCKs, for instance.
Sometimes we also say \*(L"block\*(R" to mean a lexical scope; that is, a
sequence of statements that act like a \*(L"\s-1BLOCK\s0\*(R", such as within an
eval or a file, even though the statements aren't
delimited by braces.
.IP "block buffering" 4
.IX Item "block buffering"
A method of making input and output efficient by passing one \*(L"block\*(R"
at a time.  By default, Perl does block buffering to disk files.  See
\&\*(L"buffer\*(R" and \*(L"command buffering\*(R".
.IP "Boolean" 4
.IX Item "Boolean"
A value that is either \*(L"true\*(R" or \*(L"false\*(R".
.IP "Boolean context" 4
.IX Item "Boolean context"
A special kind of \*(L"scalar context\*(R" used in conditionals to decide
whether the \*(L"scalar value\*(R" returned by an expression is \*(L"true\*(R" or
\&\*(L"false\*(R".  Does not evaluate as either a string or a number.  See
\&\*(L"context\*(R".
.IP "breakpoint" 4
.IX Item "breakpoint"
A spot in your program where you've told the debugger to stop
execution so you can poke around and see whether anything
is wrong yet.
.IP "broadcast" 4
.IX Item "broadcast"
To send a \*(L"datagram\*(R" to multiple destinations simultaneously.
.IP "\s-1BSD\s0" 4
.IX Item "BSD"
A psychoactive drug, popular in the 80s, probably developed at
U. C. Berkeley or thereabouts.  Similar in many ways to the
prescription-only medication called \*(L"System V\*(R", but infinitely more
useful.  (Or, at least, more fun.)  The full chemical name is
\&\*(L"Berkeley Standard Distribution\*(R".
.IP "bucket" 4
.IX Item "bucket"
A location in a \*(L"hash table\*(R" containing (potentially) multiple
entries whose keys \*(L"hash\*(R" to the same hash value according to its hash
function.  (As internal policy, you don't have to worry about it,
unless you're into internals, or policy.)
.IP "buffer" 4
.IX Item "buffer"
A temporary holding location for data.  Block buffering means that the data is passed on to its destination
whenever the buffer is full.  Line buffering means
that it's passed on whenever a complete line is received.  Command
buffering means that it's passed every time you do
a print command (or equivalent).  If your output is
unbuffered, the system processes it one byte at a time without the use
of a holding area.  This can be rather inefficient.
.IP "built-in" 4
.IX Item "built-in"
A \*(L"function\*(R" that is predefined in the language.  Even when hidden
by \*(L"overriding\*(R", you can always get at a built-in function by
qualifying its name with the \f(CW\*(C`CORE::\*(C'\fR pseudo-package.
.IP "bundle" 4
.IX Item "bundle"
A group of related modules on \*(L"\s-1CPAN\s0\*(R".  (Also, sometimes refers to a
group of command-line switches grouped into one \*(L"switch cluster\*(R".)
.IP "byte" 4
.IX Item "byte"
A piece of data worth eight bits in most places.
.IP "bytecode" 4
.IX Item "bytecode"
A pidgin-like language spoken among 'droids when they don't wish to
reveal their orientation (see \*(L"endian\*(R").  Named after some similar
languages spoken (for similar reasons) between compilers and
interpreters in the late 20th century.  These languages are
characterized by representing everything as a
non-architecture-dependent sequence of bytes.
.Sh "C"
.IX Subsection "C"
.IP "C" 4
.IX Item "C"
A language beloved by many for its inside-out \*(L"type\*(R" definitions,
inscrutable \*(L"precedence\*(R" rules, and heavy \*(L"overloading\*(R" of the
function-call mechanism.  (Well, actually, people first switched to C
because they found lowercase identifiers easier to read than upper.)
Perl is written in C, so it's not surprising that Perl borrowed a few
ideas from it.
.IP "C preprocessor" 4
.IX Item "C preprocessor"
The typical C compiler's first pass, which processes lines beginning
with \f(CW\*(C`#\*(C'\fR for conditional compilation and macro definition and does
various manipulations of the program text based on the current
definitions.  Also known as \fIcpp\fR(1).
.IP "call by reference" 4
.IX Item "call by reference"
An \*(L"argument\*(R"\-passing mechanism in which the \*(L"formal arguments\*(R"
refer directly to the \*(L"actual arguments\*(R", and the \*(L"subroutine\*(R" can
change the actual arguments by changing the formal arguments.  That
is, the formal argument is an \*(L"alias\*(R" for the actual argument.  See
also \*(L"call by value\*(R".
.IP "call by value" 4
.IX Item "call by value"
An \*(L"argument\*(R"\-passing mechanism in which the \*(L"formal arguments\*(R"
refer to a copy of the \*(L"actual arguments\*(R", and the \*(L"subroutine\*(R"
cannot change the actual arguments by changing the formal arguments.
See also \*(L"call by reference\*(R".
.IP "callback" 4
.IX Item "callback"
A \*(L"handler\*(R" that you register with some other part of your program
in the hope that the other part of your program will \*(L"trigger\*(R" your
handler when some event of interest transpires.
.IP "canonical" 4
.IX Item "canonical"
Reduced to a standard form to facilitate comparison.
.IP "capturing" 4
.IX Item "capturing"
The use of parentheses around a \*(L"subpattern\*(R" in a \*(L"regular
expression\*(R" to store the matched \*(L"substring\*(R" as a \*(L"backreference\*(R".
(Captured strings are also returned as a list in \*(L"list context\*(R".)
.IP "character" 4
.IX Item "character"
A small integer representative of a unit of orthography.
Historically, characters were usually stored as fixed-width integers
(typically in a byte, or maybe two, depending on the character set),
but with the advent of \s-1UTF\-8\s0, characters are often stored in a
variable number of bytes depending on the size of the integer that
represents the character.  Perl manages this transparently for you,
for the most part.
.IP "character class" 4
.IX Item "character class"
A square-bracketed list of characters used in a \*(L"regular expression\*(R"
to indicate that any character of the set may occur at a given point.
Loosely, any predefined set of characters so used.
.IP "character property" 4
.IX Item "character property"
A predefined \*(L"character class\*(R" matchable by the \f(CW\*(C`\ep\*(C'\fR
\&\*(L"metasymbol\*(R".  Many standard properties are defined for \*(L"Unicode\*(R".
.IP "circumfix operator" 4
.IX Item "circumfix operator"
An \*(L"operator\*(R" that surrounds its \*(L"operand\*(R", like the angle
operator, or parentheses, or a hug.
.IP "class" 4
.IX Item "class"
A user-defined \*(L"type\*(R", implemented in Perl via a \*(L"package\*(R" that
provides (either directly or by inheritance) methods (that
is, subroutines) to handle instances of
the class (its objects).  See also \*(L"inheritance\*(R".
.IP "class method" 4
.IX Item "class method"
A \*(L"method\*(R" whose \*(L"invocant\*(R" is a \*(L"package\*(R" name, not an
\&\*(L"object\*(R" reference.  A method associated with the class as a whole.
.IP "client" 4
.IX Item "client"
In networking, a \*(L"process\*(R" that initiates contact with a \*(L"server\*(R"
process in order to exchange data and perhaps receive a service.
.IP "cloister" 4
.IX Item "cloister"
A \*(L"cluster\*(R" used to restrict the scope of a \*(L"regular expression
modifier\*(R".
.IP "closure" 4
.IX Item "closure"
An \*(L"anonymous\*(R" subroutine that, when a reference to it is generated
at run time, keeps track of the identities of externally visible
lexical variables even after those lexical
variables have supposedly gone out of \*(L"scope\*(R".  They're called
\&\*(L"closures\*(R" because this sort of behavior gives mathematicians a sense
of closure.
.IP "cluster" 4
.IX Item "cluster"
A parenthesized \*(L"subpattern\*(R" used to group parts of a \*(L"regular