MAN page from Mandriva 2007 perl-5.8.8-7.1mdv2007.0.i586.rpm

Encode::Alias

Section: Perl Programmers Reference Guide (3pm)
Updated: 2001-09-21
Index

NAME

Encode::Alias - alias definitions to encodings

SYNOPSIS

  use Encode;  use Encode::Alias;  define_alias( newName => ENCODING);

DESCRIPTION

Allows newName to be used as an alias for ENCODING. ENCODING may beeither the name of an encoding or an encoding object (as described in Encode).

Currently newName can be specified in the following ways:

As a simple string.

As a qr// compiled regular expression, e.g.:

  define_alias( qr/^iso8859-(\d+)$/i => '"iso-8859-$1"' );

In this case, if ENCODING is not a reference, it is "eval"-edin order to allow $1 etc. to be substituted. The example is oneway to alias names as used in X11 fonts to the MIME names for theiso-8859-* family. Note the double quotes inside the single quotes.

(or, you don't have to do this yourself because this example is predefined)

If you are using a regex here, you have to use the quotes as shown orit won't work. Also note that regex handling is tricky even for theexperienced. Use this feature with caution.

As a code reference, e.g.:

  define_alias( sub {shift =~ /^iso8859-(\d+)$/i ? "iso-8859-$1" : undef } );

The same effect as the example above in a different way. The codereftakes the alias name as an argument and returns a canonical name onsuccess or undef if not. Note the second argument is not required.Use this with even more caution than the regex version.

Changes in code reference aliasing

As of Encode 1.87, the older form

  define_alias( sub { return  /^iso8859-(\d+)$/i ? "iso-8859-$1" : undef } );

no longer works.

Encode up to 1.86 internally used ``local $_'' to implement ths olderform. But consider the code below;

  use Encode;  $_ = "eeeee" ;  while (/(e)/g) {    my $utf = decode('aliased-encoding-name', $1);    print "position:",pos,"\n";  }

Prior to Encode 1.86 this fails because of ``local $_''.

Alias overloading

You can override predefined aliases by simply applying define_alias().The new alias is always evaluated first, and when necessary,define_alias() flushes the internal cache to make the new definitionavailable.

  # redirect SHIFT_JIS to MS/IBM Code Page 932, which is a  # superset of SHIFT_JIS

  define_alias( qr/shift.*jis$/i  => '"cp932"' );  define_alias( qr/sjis$/i        => '"cp932"' );

If you want to zap all predefined aliases, you can use

  Encode::Alias->undef_aliases;

to do so. And

  Encode::Alias->init_aliases;

gets the factory settings back.

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