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Jarkko Hietaniemi


utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source code


    use utf8;
    no utf8;


The use utf8 pragma tells the Perl parser to allow UTF-8 in the program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based platforms). The no utf8 pragma tells Perl to switch back to treating the source text as literal bytes in the current lexical scope.

This pragma is primarily a compatibility device. Perl versions earlier than 5.6 allowed arbitrary bytes in source code, whereas in future we would like to standardize on the UTF-8 encoding for source text. Until UTF-8 becomes the default format for source text, this pragma should be used to recognize UTF-8 in the source. When UTF-8 becomes the standard source format, this pragma will effectively become a no-op. For convenience in what follows the term UTF-X is used to refer to UTF-8 on ASCII and ISO Latin based platforms and UTF-EBCDIC on EBCDIC based platforms.

Enabling the utf8 pragma has the following effect:

  • Bytes in the source text that have their high-bit set will be treated as being part of a literal UTF-8 character. This includes most literals such as identifiers, string constants, constant regular expression patterns and package names. On EBCDIC platforms characters in the Latin 1 character set are treated as being part of a literal UTF-EBCDIC character.

Note that if you have bytes with the eighth bit on in your script (for example embedded Latin-1 in your string literals), use utf8 will be unhappy since the bytes are most probably not well-formed UTF-8. If you want to have such bytes and use utf8, you can disable utf8 until the end the block (or file, if at top level) by no utf8;.

Utility functions

The following functions are defined in the utf8:: package by the perl core.

  • $num_octets = utf8::upgrade($string);

    Converts internal representation of string to the Perl's internal UTF-X form. Returns the number of octets necessary to represent the string as UTF-X.

  • utf8::downgrade($string[, CHECK])

    Converts internal representation of string to be un-encoded bytes.

  • utf8::encode($string)

    Converts (in-place) $string from logical characters to octet sequence representing it in Perl's UTF-X encoding.

  • $flag = utf8::decode($string)

    Attempts to convert $string in-place from Perl's UTF-X encoding into logical characters.

utf8::encode is like utf8::upgrade but the UTF8 flag does not get turned on. See perlunicode for more on the UTF8 flag and the C API functions sv_utf8_upgrade, sv_utf8_downgrade, sv_utf8_encode, sv_utf8_decode that are wrapped by the Perl functions utf8::upgrade, utf8::downgrade, utf8::encode and utf8::decode.


perlunicode, bytes