|Perl Language Reference Manual|
by Larry Wall and others
Paperback (6"x9"), 724 pages
RRP £29.95 ($39.95)
Sales of this book support The Perl Foundation! Get a printed copy>>>
7.22 Comma Operator
Binary "," is the comma operator. In scalar context it evaluates its left argument, throws that value away, then evaluates its right argument and returns that value. This is just like C's comma operator.
In list context, it's just the list argument separator, and inserts both its arguments into the list. These arguments are also evaluated from left to right.
=> operator is a synonym for the comma except that it causes
its left operand to be interpreted as a string if it begins with a letter
or underscore and is composed only of letters, digits and underscores.
This includes operands that might otherwise be interpreted as operators,
constants, single number v-strings or function calls. If in doubt about
this behaviour, the left operand can be quoted explicitly.
=> operator behaves exactly as the comma operator
or list argument separator, according to context.
use constant FOO => "something"; my %h = ( FOO => 23 );
is equivalent to:
my %h = ("FOO", 23);
It is NOT:
my %h = ("something", 23);
=> operator is helpful in documenting the correspondence
between keys and values in hashes, and other paired elements in lists.
%hash = ( $key => $value ); login( $username => $password );
|ISBN 9781906966027||Perl Language Reference Manual||See the print edition|