Subroutines, Packages and Modules

&SUBROUTINE LIST

Executes a SUBROUTINE declared by a sub declaration, and returns the value of the last expression evaluated in SUBROUTINE. SUBROUTINE can be an expression yielding a reference to a code object. The & may be omitted if the subroutine has been declared before being used.

bless REF [ , PACKAGE ]

Turns the object REF into an object in PACKAGE. Returns the reference.

caller [ EXPR ]

Returns an array ($package,$file,$line,...) for a specific subroutine call. caller returns this info for the current subroutine, caller(1) for the caller of this subroutine, etc. Returns false if no caller.

do SUBROUTINE LIST

Deprecated form of &SUBROUTINE.

goto &SUBROUTINE

Substitutes a call to SUBROUTINE for the current subroutine.

import MODULE [ [ VERSION ] LIST ]

Imports the named subroutines from MODULE.

no MODULE [ LIST ]

Cancels imported semantics. See use.

package NAME

Designates the remainder of the current block as a package.

require EXPR†

If EXPR is numeric, requires Perl to be at least that version. Otherwise EXPR must be the name of a file that is included from the Perl library. Does not include more than once, and yields a fatal error if the file does not evaluate to a true value. If EXPR is a bare word, assumes extension .pm for the name of the file.

return EXPR

Returns from a subroutine with the value specified.

sub NAME { EXPR ; ... }

Designates NAME as a subroutine. Parameters are passed by reference as array @_. Returns the value of the last expression evaluated.

[ sub ] BEGIN { EXPR ; ... }

Defines a setup BLOCK to be called before execution.

[ sub ] END { EXPR ; ... }

Defines a cleanup BLOCK to be called upon termination.

tie VAR, PACKAGE, [ LIST ]

Ties a variable to a package that will handle it. Can be used to bind a dbm or ndbm file to a hash.

untie VAR

Breaks the binding between the variable and the package.

use MODULE [ [ VERSION ] LIST ]

Imports semantics from the named module into the current package.

Object-Oriented Programming

Perl rules of object oriented programming:

• An object is simply a reference that happens to know which class it belongs to. Objects are blessed, references are not.
• A class is simply a package that happens to provide methods to deal with object references. If a package fails to provide a method, the base classes as listed in @ISA are searched.
• A method is simply a subroutine that expects an object reference (or a package name, for static methods) as the first argument.

Methods can be applied with:

METHOD OBJREF PARAMETERS           or
OBJREF->METHOD PARAMETERS

Conversion Functions

chr EXPR†

Returns the character represented by the decimal value EXPR.

gmtime EXPR†

Converts a time as returned by the time function to a 9-element array (0: $sec, 1: $min, 2: $hour, 3: $mday, 4: $mon, 5: $year, 6: $wday, 7: $yday, 8: $isdst) with the time analyzed for the Greenwich time zone. $mon has the range 0..11 and $wday has the range 0..6.

hex EXPR†

Returns the decimal value of EXPR interpreted as a hex string.

localtime EXPR†

Converts a time as returned by the time function to ctime(3) string. In array context, returns a 9-element array with the time analyzed for the local time zone.

oct EXPR†

Returns the decimal value of EXPR interpreted as an octal string. If EXPR starts off with 0x, interprets it as a hex string instead.

ord EXPR†

Returns the ASCII value of the first character of EXPR.

vec EXPR, OFFSET, BITS

Treats string EXPR as a vector of unsigned integers, and yields the bit at OFFSET. BITS must be between 1 and 32. May be assigned to.

Structure Conversion
pack TEMPLATE, LIST
Packs the values into a binary structure using TEMPLATE.
unpack TEMPLATE, EXPR
Unpacks the structure EXPR into an array, using TEMPLATE.

TEMPLATE is a sequence of characters as follows: