% perldoc perl
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Reference Manual
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perlvar Perl predefined variables
perlre Perl regular expressions, the rest of the story
% perldoc perlvar
$/ 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.
(Mnemonic: / delimits line boundaries when quoting poetry.)
