=head1 NAME
perlglossary - Perl Glossary
=head1 DESCRIPTION
A glossary of terms (technical and otherwise) used in the Perl documentation.
Other useful sources include the Free On-Line Dictionary of Computing
L, the Jargon File
L, and Wikipedia L.
=head2 A
=over 4
=item accessor methods
A L used to indirectly inspect or update an L's
state (its L).
=item actual arguments
The L that you supply to a L
or L when you call it. For instance, when you call
C, the string C<"puff"> is the actual argument. See
also L and L.
=item address operator
Some languages work directly with the memory addresses of values, but
this can be like playing with fire. Perl provides a set of asbestos
gloves for handling all memory management. The closest to an address
operator in Perl is the backslash operator, but it gives you a L, which is much safer than a memory address.
=item algorithm
A well-defined sequence of steps, clearly enough explained that even a
computer could do them.
=item alias
A nickname for something, which behaves in all ways as though you'd
used the original name instead of the nickname. Temporary aliases are
implicitly created in the loop variable for C loops, in the
C<$_> variable for L or L
operators, in C<$a> and C<$b> during L's
comparison function, and in each element of C<@_> for the L of a subroutine call. Permanent aliases are explicitly
created in L by L symbols or by
assignment to L. Lexically scoped aliases for
package variables are explicitly created by the L
declaration.
=item alternatives
A list of possible choices from which you may select only one, as in
"Would you like door A, B, or C?" Alternatives in regular expressions
are separated with a single vertical bar: C<|>. Alternatives in
normal Perl expressions are separated with a double vertical bar:
C<||>. Logical alternatives in L expressions are separated
with either C<||> or C.
=item anonymous
Used to describe a L that is not directly accessible
through a named L. Such a referent must be indirectly
accessible through at least one L. When the last
hard reference goes away, the anonymous referent is destroyed without
pity.
=item architecture
The kind of computer you're working on, where one "kind" of computer
means all those computers sharing a compatible machine language.
Since Perl programs are (typically) simple text files, not executable
images, a Perl program is much less sensitive to the architecture it's
running on than programs in other languages, such as C, that are
compiled into machine code. See also L and L.
=item argument
A piece of data supplied to a L,
L, L, or L to tell it what it's
supposed to do. Also called a "parameter".
=item ARGV
The name of the array containing the L L from the
command line. If you use the empty C<< EE >> operator, L is
the name of both the L used to traverse the arguments and
the L containing the name of the current input file.
=item arithmetical operator
A L such as C<+> or C that tells Perl to do the arithmetic
you were supposed to learn in grade school.
=item array
An ordered sequence of L, stored such that you can
easily access any of the values using an integer L
that specifies the value's L in the sequence.
=item array context
An archaic expression for what is more correctly referred to as
L.
=item ASCII
The American Standard Code for Information Interchange (a 7-bit
character set adequate only for poorly representing English text).
Often used loosely to describe the lowest 128 values of the various
ISO-8859-X character sets, a bunch of mutually incompatible 8-bit
codes sometimes described as half ASCII. See also L.
=item assertion
A component of a L that must be true for the
pattern to match but does not necessarily match any characters itself.
Often used specifically to mean a L assertion.
=item assignment
An L whose assigned mission in life is to change the value
of a L.
=item assignment operator
Either a regular L, or a compound L composed
of an ordinary assignment and some other operator, that changes the
value of a variable in place, that is, relative to its old value. For
example, C<$a += 2> adds C<2> to C<$a>.
=item associative array
See L. Please.
=item associativity
Determines whether you do the left L first or the right
L first when you have "A L B L C" and
the two operators are of the same precedence. Operators like C<+> are
left associative, while operators like C<**> are right associative.
See L for a list of operators and their associativity.
=item asynchronous
Said of events or activities whose relative temporal ordering is
indeterminate because too many things are going on at once. Hence, an
asynchronous event is one you didn't know when to expect.
=item atom
A L component potentially matching a
L containing one or more characters and treated as an
indivisible syntactic unit by any following L. (Contrast
with an L that matches something of L and may
not be quantified.)
=item atomic operation
When Democritus gave the word "atom" to the indivisible bits of
matter, he meant literally something that could not be cut: I
(not) + I (cuttable). An atomic operation is an action that
can't be interrupted, not one forbidden in a nuclear-free zone.
=item attribute
A new feature that allows the declaration of L
and L with modifiers as in C. Also, another name for an L of an
L.
=item autogeneration
A feature of L of L, whereby
the behavior of certain L 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 L.
=item autoincrement
To add one to something automatically, hence the name of the C<++>
operator. To instead subtract one from something automatically is
known as an "autodecrement".
=item autoload
To load on demand. (Also called "lazy" loading.) Specifically, to
call an L subroutine on behalf of an
undefined subroutine.
=item autosplit
To split a string automatically, as the B<-a> L does when
running under B<-p> or B<-n> in order to emulate L. (See also
the L module, which has nothing to do with the B<-a>
switch, but a lot to do with autoloading.)
=item autovivification
A Greco-Roman word meaning "to bring oneself to life". In Perl,
storage locations (L) spontaneously generate
themselves as needed, including the creation of any L
values to point to the next level of storage. The assignment
C<$a[5][5][5][5][5] = "quintet"> 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.
=item AV
Short for "array value", which refers to one of Perl's internal data
types that holds an L. The L type is a subclass of
L.
=item awk
Descriptive editing term--short for "awkward". Also coincidentally
refers to a venerable text-processing language from which Perl derived
some of its high-level ideas.
=back
=head2 B
=over 4
=item backreference
A substring L by a subpattern within
unadorned parentheses in a L, also referred to as a capture group. The
sequences (C<\g1>, C<\g2>, etc.) later in the same pattern refer back to
the corresponding subpattern in the current match. Outside the pattern,
the numbered variables (C<$1>, C<$2>, etc.) continue to refer to these
same values, as long as the pattern was the last successful match of
the current dynamic scope. C<\g{-1}> can be used to refer to a group by
relative rather than absolute position; and groups can be also be named, and
referred to later by name rather than number. See L.
=item backtracking
The practice of saying, "If I had to do it all over, I'd do it
differently," 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, and
its earlier attempts don't pan out. See L.
=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.
=item bareword
A word sufficiently ambiguous to be deemed illegal under L