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HANDLE->input_record_separator( EXPR )

The input record separator, newline by default. This influences Perl's idea of what a "line" is. Works like awk's RS variable, including treating empty lines as a terminator if set to the null string (an empty line cannot contain any spaces or tabs). You may set it to a multi-character string to match a multi-character terminator, or to undef to read through the end of file. Setting it to "\n\n" means something slightly different than setting to "", if the file contains consecutive empty lines. Setting to "" will treat two or more consecutive empty lines as a single empty line. Setting to "\n\n" will blindly assume that the next input character belongs to the next paragraph, even if it's a newline.

local $/;           # enable "slurp" mode
local $_ = <FH>;    # whole file now here
s/\n[ \t]+/ /g;

Remember: the value of $/ is a string, not a regex. awk has to be better for something. :-)

Setting $/ to a reference to an integer, scalar containing an integer, or scalar that's convertible to an integer will attempt to read records instead of lines, with the maximum record size being the referenced integer. So this:

local $/ = \32768; # or \"32768", or \$var_containing_32768
open my $fh, "<", $myfile or die $!;
local $_ = <$fh>;

will read a record of no more than 32768 bytes from FILE. If you're not reading from a record-oriented file (or your OS doesn't have record-oriented files), then you'll likely get a full chunk of data with every read. If a record is larger than the record size you've set, you'll get the record back in pieces. Trying to set the record size to zero or less will cause reading in the (rest of the) whole file.

On VMS only, record reads bypass PerlIO layers and any associated buffering,so you must not mix record and non-record reads on the same filehandle. Record mode mixes with line mode only when the same buffering layer is in use for both modes.

If you perform a record read on a FILE with an encoding layer such as :encoding(latin1) or :utf8, you may get an invalid string as a result, may leave the FILE positioned between characters in the stream and may not be reading the number of bytes from the underlying file that you specified. This behaviour may change without warning in a future version of perl.

See also "Newlines" in perlport. Also see "$.".

Mnemonic: / delimits line boundaries when quoting poetry.