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Computer languages vary in how many and what kinds of data types they
provide at compile time. Unlike some commonly used languages that
provide many types for similar kinds of values, Perl provides just
a few built-in data types. (You can, however, define fancy dynamic types
via the object-oriented features of Perl--see Chapter 5, Packages, Modules, and Object Classes.) Perl has
three basic data types: scalars, arrays of scalars, and hashes
of scalars, also known as associative arrays.
Scalars are the fundamental type from which more complicated structures
are built. A scalar stores a single, simple value, typically a string
or a number. Elements of this simple type can be combined into either
of the two composite types. An array is an ordered list of scalars that you
access with a numeric subscript (subscripts start at 0).[1]
A hash is an unordered set of key/value pairs that you access using
strings (keys) as subscripts, to look up the scalar value corresponding to
a given
key. Variables are always one of these three types. (Other than
variables, Perl also has some partially hidden thingies called
filehandles, directory handles, subroutines, typeglobs, and formats,
which you can think of as data types.)
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