String Processing with Perl - Jumping Jacks (Page 2 of 8 )
We'll begin right at the top, with some very basic definitions and concepts.
In Perl, the term "string" refers to a sequence of characters. The following are all valid examples of strings:
"I'm back!"
"by golly miss molly"
"a long time ago in a galaxy far, far away"
String values can be assigned to a variable using the standard assignment operator.
$identity = "Jedi";
String values may be enclosed in either double quotes ("") or single quotes('') - the following variable assignments are equivalent"
$character = "Luke";
$character = 'Luke';
String values enclosed in double quotes are automatically parsed for variable names; if variable names are found, they are automatically replaced with the appropriate variable value.
#!/usr/bin/perl
$character = "Chewbacca";
$race = "Wookie";
# this would contain the string "Chewbacca is a Wookie" $sentence =
"$character is a $race";
Perl also allows you to create strings which span multiple lines. The original formatting of the string, including newlines and whitespace, is retained when such a string is printed.
# multi-line block
$html_output = <<EOF;
<html>
<head></head>
<body>
<ul>
<li>Human
<li>Wookie
<li>Ewok
</ul>
</body>
</html>
EOF
The << symbol indicates to Perl that what comes next is a multi-line block of text, and should be printed as is right up to the marker "EOF". This comes in very handy when you need to output a chunk of HTML code, or any other multi-line string.
Strings can be concatenated with the string concatenation operator, represented by a period(.)
#!/usr/bin/perl
# set up some string variables
$a = "the cow ";
$b = "jumped over ";
$c = "the moon ";
# combine them using the concatenation operator
# this returns "the cow jumped over the moon"
$statement = $a . $b . $c;
# and this returns "the moon jumped over the cow"
$statement = $c . $b . $a;
Note that if your string contains quotes, carriage returns or backslashes, it's necessary to escape these special characters with a backslash.
# will cause an error due to mismatched quotes
$film = 'America's Sweethearts';
# will be fine
$film = 'America\'s Sweethearts';
The print() function is used to output a string or string variable.
#!/usr/bin/perl
# string
print "Last Tango In Paris";
# string variable
$film = "Last Tango In Paris";
print $film;
But if you thought that all you can do is concatenate and print strings, think again - you can also repeat strings with the repetition operator, represented by the character x.
#!/usr/bin/perl
# set a string variable
$insult = "Loser!\n";
# repeat it
print($insult x 7);
Here's the output:
Loser!
Loser!
Loser!
Loser!
Loser!
Loser!
Loser!
Nasty, huh?
Next: Choppy Waters >>
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