Tony Cook

Perl 5.18 will ship with a change in behaviour when using getline() (aka the <$handle> operator) on handles marked as returning Unicode where $/ is a reference to an integer.

If you're not familar with the behaviour, for a file with no PerlIO layers:

$/ = \500;
my $x = <$fh>; # read 500 bytes

This won't change in 5.18, but it will if the stream has a layer that internally returns unicode, such as any of:

• :encoding(iso-8859-1)
• :encoding(utf-16)
• :encoding(utf-8) (ok, any :encoding stream)
• :utf8

In 5.16 and earlier, getline() will read the specified number of bytes from the stream, even if that would fall in the middle of a character.

This leads to a few problems:

• the result can be a UTF-8 marked scalar that doesn't contain valid UTF-8.
• the input stream can be left on a non-character boundary.
• the record read only corresponds to bytes in the file if the file is UTF-8.

From 5.18, getline($fh) will behave like read($fh, $out, $$\) -- the specified number of characters will be read from the stream instead of the specified number of bytes.

For more details (and arguments), see perlbug ticket 79960.