Encode::Alias(3perl) Perl Programmers Reference Guide Encode::Alias(3perl)
NAME
Encode::Alias - alias definitions to encodings
SYNOPSIS
use Encode;
use Encode::Alias;
define_alias( "newName" => ENCODING);
define_alias( qr/.../ => ENCODING);
define_alias( sub { return ENCODING if ...; } );
DESCRIPTION
Allows newName to be used as an alias for ENCODING. ENCODING may be
either the name of an encoding or an encoding object (as described in
Encode).
Currently the first argument to define_alias() 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"-ed in
order to allow $1 etc. to be substituted. The example is one way to
alias names as used in X11 fonts to the MIME names for the
iso-8859-* family. Note the double quotes inside the single quotes.
(or, you don't have to do this yourself because this example is
predefined)
If you are using a regex here, you have to use the quotes as shown
or it won't work. Also note that regex handling is tricky even for
the experienced. Use this feature with caution.
As a code reference, e.g.:
define_alias( sub {shift =~ /^iso8859-(\d+)$/i ? "iso-8859-$1" : undef } );
The same effect as the example above in a different way. The
coderef takes the alias name as an argument and returns a canonical
name on success or undef if not. Note the second argument is
ignored if provided. Use this with even more caution than the regex
version.
Changes in code reference aliasing
As of Encode 1.87, the older form
define_alias( sub { return /^iso8859-(\d+)$/i ? "iso-8859-$1" : undef } );
no longer works.
Encode up to 1.86 internally used "local $_" to implement this older
form. 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 $_".
Alias overloading
You can override predefined aliases by simply applying define_alias().
The new alias is always evaluated first, and when necessary,
define_alias() flushes the internal cache to make the new definition
available.
# redirect SHIFT_JIS to MS/IBM Code Page 932, which is a
# superset of SHIFT_JIS
define_alias( qr/shift.*jis$/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.
Note that define_alias() will not be able to override the canonical name
of encodings. Encodings are first looked up by canonical name before
potential aliases are tried.
SEE ALSO
Encode, Encode::Supported
perl v5.40.1 2026-08-30 Encode::Alias(3perl)
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