Indicates with internal storage format is used by a scalar.

USE: Debugging XS modules.

Changes a scalar to use the upgraded string format (if it's not already) without changing the string.

my $s = ...;

my $t = $s;
utf8::upgrade( $t );

say utf8::is_utf8( $t ) ?1:0;   # 1
say $s eq $t            ?1:0;   # 1
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USE: Working around instances of The Unicode Bug.

Changes a scalar to use the downgraded string format (if it's not already) without changing the string. Dies if it can't.

my $s = ...;

my $t = $s;
utf8::downgrade( $t );          # Might croak

say utf8::is_utf8( $t ) ?1:0;   # 0
say $s eq $t            ?1:0;   # 1
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USE: Working around instances of The Unicode Bug.

Encodes a string using utf8.

Expects a string of arbitrary characters in either storage format.

Produces a string of 8-bit characters in the downgraded format.

USE: You should probably be encoding using the standard UTF-8 encoding instead of the Perl-specific utf8 encoding.

Decodes a string encoded using utf8. Dies if it can't.

Expects a string of 8-bit characters in either storage format.

Produces a string of characters in the upgraded format.

USE: utf8 is a Perl-specific encoding. Are sure the text isn't encode using the standard UTF-8 encoding?

Indicates with internal storage format is used by a scalar.

USE: You might as well use the equivalent built-in utf8::is_utf8.

Mostly equivalent to the following:

utf8::decode( $_ ) if !utf8::is_utf8( $_ );
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The difference is that it produces a corrupt scalar if the string isn't valid utf8.

USE: Do not use as it introduces The Unicode Bug.

Equivalent to the following:

utf8::encode( $_ ) if utf8::is_utf8( $_ );
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USE: Do not use as it introduces The Unicode Bug.