The concept of PERL escape code is the same as HTML escape code. It is a way to enter a specific feature or character "outside" of the normal coding (usually to appear on the web page itself).

For example... to show double quotes on the web page :

Regular document	HTML Escape	PERL Escape
"	"	\"

Quick examples :

Coding input :	"Hello 'World'" "Hello \'"World\""
Page output :	Hello 'World' Hello "World"

Common escape sequences :

\a	Beep
\b	Backspace
\c	"Control" caracter. \cD = CTRL-D
\e	Escape
\f	Form feed
\l	Make the next letter lowercase
\n	New line, return.
\r	Carriage return.
\t	Tab.
\u	Make the next letter uppercase
\x	Enables hex numbers
\v	Vertical tab
\\	Print backslash
\"	Print double quotes
\	Escape next character if known otherwise print. Also allows octal numbers.
\L	Make all letters lowercase until the \E
\U	Make all letters uppercase until the \E
\Q	Add a backslash-quote to all the nonalphanumerics until the \E
\E	Terminates the effects of \L, \U, or \Q

The TAB and NEW LINE escapes are the most commonly used.