Programming Perl, 4th Edition

open

use open IN  => ":crlf", OUT => ":raw";
use open OUT => ":utf8";
use open IO  => ":encoding(iso–8859–7)";

use open IO  => ":locale";

use open ":encoding(utf8)";
use open ":locale";
use open ":encoding(iso–8859–7)";

use open ":std";

The open pragma declares one or more default layers (formerly called disciplines) for I/O operations, but only if your Perl binary was built with PerlIO. Any open and readpipe (that is, qx// or backticks) operators found within the lexical scope of this pragma that do not specify their own layers will use the declared defaults. Neither open with an explicit set of layers, nor sysopen under any circumstances, is influenced by this pragma.

There are several layers to choose from:

:bytes

This layer treats the data as characters with codepoints in the range 0 to 255. This is the inverse of the :utf8 layer. This is not the same thing as :raw, though, since this still may do CRLF processing under Windows systems.

:crlf

This layer corresponds to the text mode, in which line endings are translated to or from the native line endings. This is a no-op on a platform where binmode is a no-op. This layer is available without PerlIO.

:encoding(ENCODING)

This layer specifies any encoding supported by the Encode module, directly or indirectly.

:locale

This layer decodes or encodes its data according to the locale settings.

:raw

This pseudolayer turns off any layer below it that would interpret the data as other than binary data. This is a no-op on a platform where binmode is a ...