Programming Perl, 4th Edition

String Literals

String literals are usually surrounded by either single or double quotes. They work much like Unix shell quotes: double-quoted string literals are subject to backslash and variable interpolation, but single-quoted strings are not (except for \' and \\ so that you can embed single quotes and backslashes into single-quoted strings). If you want to embed any other backslash sequences such as \n (newline), you must use the double-quoted form. (Backslash sequences are also known as escape sequences, because you “escape” the normal interpretation of characters temporarily.)

A single-quoted string must be separated from a preceding word by a space because a single quote is a valid—though archaic—character in an identifier. Its use has been replaced by the more visually distinct :: sequence. That means that $main'var and $main::var are the same thing, but the second is generally considered easier to read for people and programs.

Double-quoted strings are subject to various forms of character interpolation, as listed in Table 2-5. Many of these will be familiar to programmers of other languages.

Table 2-5. Backslashed character escapes

Code	Meaning
\n	Newline (usually LF)
\r	Carriage return (usually CR)
\t	Horizontal tab
\f	Form feed
\b	Backspace
\a	Alert (bell)
\e	ESC character
\033	ESC in octal
\o{33}	Also ESC in octal
\x7f	DEL in hexadecimal
\x{263a}	Character number 0x263A
\N{LATIN SMALL LETTER E WITH ACUTE}	The named character latin small letter e with acute, “é”, which is ...