$#days # the last index of array arrays (and slices of arrays and hashes) are denoted by which works much as the word "these" or "those" does in English, in that it indicates multiple values are expected. $days # the 29th element of array the 'Feb' value from hash %days The '$' symbol works semantically like the English word "the" in that it indicates a single value is expected. Scalar values are always named with '$', even when referring to a scalar that is part of an array or a hash.
PERL LENGTH OF ARRAY WINDOWS
In addition, several special variables that provide windows into the inner working of Perl have names containing punctuation characters. Strings that match parenthesized parts of a regular expression are saved under names containing only digits after the $ (see perlop and perlre). They have strange names so they don't accidentally collide with one of your normal variables. Perl also has its own built-in variables whose names don't follow these rules. This is described in more detail below and in perlref. It's possible to substitute for a simple identifier, an expression that produces a reference to the value at runtime. For a more in-depth discussion on identifiers, see "Identifier parsing". In some cases, it may be a chain of identifiers, separated by :: (or by the slightly archaic ') all but the last are interpreted as names of packages, to locate the namespace in which to look up the final identifier (see "Packages" in perlmod for details). Usually this name is a single identifier, that is, a string beginning with a letter or underscore, and containing letters, underscores, and digits. The rest of the name tells you the particular value to which it refers. The first character of the name tells you to what sort of data structure it refers. Values are usually referred to by name, or through a named reference. Hashes are unordered collections of scalar values indexed by their associated string key.
Normal arrays are ordered lists of scalars indexed by number, starting with 0.
A scalar is a single string (of any size, limited only by the available memory), number, or a reference to something (which will be discussed in perlref). Perl has three built-in data types: scalars, arrays of scalars, and associative arrays of scalars, known as "hashes". Perldata - Perl data types #DESCRIPTION # Variable names Special floating point: infinity (Inf) and not-a-number (NaN).
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