This section describes what is an expression, a mixture of values, variables, operations of expressions and function calls. A tutorial example is provided to show you examples of expressions..
An expression is a mixture of values, operations of expressions and function calls that can be evaluated to a value.
Examples of expressions are:
A scalar value is an expression: 9.99, "Hello world!", ...
A list value is an expression: ("PI", 3.14, "Price", 9.99), ...
The undef value is an expression: undef
A scalar, array, or hash variable is an expression: $price, @links, %siteRanks, ...
An arithmetic operation is an expression: 1+2, 1/3, $price * 5, ...
A string concatenation operation is an expression: "Hello ".$name, ...
A comparison operation is an expression: $sales > $expenses, $price == undef, ...
A function call is an expression: sort(@links), undef($price), ...
A list value subscription is an expression: ('Mon','Tue','Wed')[1], ...
A array variable subscription is an expression: $links[1], ...
A hash variable subscription is an expression: $siteRanks{"herongyang.com"}, ...
An expression can have multiple operations: $capital*(1+$interest)**$years, ...
There are many more types of expression examples not listed above.
Here is a Perl tutorial script showing you examples of expressions:
#- Expression.pl
#- Copyright (c) 1995 by Dr. Herong Yang, http://www.herongyang.com/
#
print(9.99, "\n"); # A scalar numeric value
print("Hello world!", "\n"); # A scalar string value
print(("PI", 3.14, "Price", 9.99), "\n");
# A list value
print(undef, "\n"); # The undef value
$price = 9.99;
print($price, "\n"); # A scalar variable
@links = ("herongyang.com", "perl.org", "cpan.org");
print(@links, "\n"); # An array variable
%siteRanks = ("herongyang.com", 4, "perl.org", 6, "google.com", 9);
print(%siteRanks, "\n"); # A hash variable
print($price*5, "\n"); # An arithmetic operation
$name = "Herong";
print("Hello ".$name, "\n"); # A string concatenation
$sales = 876.54;
$expenses = 654.32;
print($sales>$expenses, "\n"); # A comparison operation
print(sort(@links), "\n"); # A function call
print(('Mon','Tue','Wed')[1], "\n");
# A list value subscription
print($links[1], "\n"); # An array subscription
print($siteRanks{"herongyang.com"}, "\n");
# A hash subscription
$capital = 100.00;
$interest = 0.0475;
$years = 5;
print($capital*(1+$interest)**$years, "\n");
# Multiple operations
