In perl there are two ways to represent string literals: single-quoted strings and double-quoted strings.

Single-Quoted Strings

Single quoted are a sequence of characters that begin and end with a single quote. These quotes are not a part of the string they just mark the beginning and end for the Perl interpreter. If you want a ' inside of your string you need to preclude it with a \ like this \' as you'll see below. Let's see how this works below.
'four'       #has four letters in the string
'can\'t'     #has five characters and represents "can't"
'hi\there'   #has eight characters and represents"hi\\there" (one \ in the string)
'blah\\blah' #has nine characters and represents "blah\\blah" (one \ in the string)
If you want to put a new line in a single-quoted string it goes something like this
line2'       #has eleven characters line1, newline character, and then line2
Single-quoted strings don't interpret \n as a newline.

Double-Quoted Strings
Double quoted strings act more like strings in C or C++ the backslash allows you to represent control characters. Another nice feature Double-Quoted strings offers is variable interpolation this substitutes the value of a variable into the string. Some examples are below
$word="hello";             #$word becomes hello
$statement="$word world";  #variable interpolation, $statement becomes "hello world"
"Hello World\n";           #"Hello World" followed by a newline

Some of the things you can put in a Double-Quoted String
RepresentationWhat it Means
\"Double quote
\007octal ascii value this time 007 or the bell
\x07hex ascii value this time 007 or the bell
\cDany control character.. here it is control-D
\llowercase next letter
\uuppercase next letter
\Llowercase all letters until \E
\Uuppercase all letters until \E
\QBackslash quote all nonletters and nonnumbers until \E
\EStop \U \L or \Q