Mastering Perl for Bioinformatics [Electronic resources] نسخه متنی

A.4 Assignment

Scalar variables
are
assigned
scalar values with an assignment
operator (the equals sign) in an
assignment
statement:

$thousand = 1000;

assigns the integer 1000, a scalar value, to the scalar variable
$thousand.

The assignment statement looks like an equal sign from elementary
mathematics, but its meaning is different. The assignment statement
is an instruction, not an assertion. It doesn't mean
"$thousand equals
1000." It means "store the scalar
value 1000 into the scalar variable
$thousand". However, after the
statement, the value of the scalar variable
$thousand is, indeed, equal to 1000.

References are usually saved in scalar variables. For example:

$pi = \3.14159265;

If you try to print $pi after this assignment, you
get an indication that it's a reference to a scalar
value at a memory location represented in hexadecimal digits. To
print the value of a variable that's a reference to
a scalar, precede its name with an additional dollar sign:

print $pi,"\n";
print $$pi, "\n";

This gives the output:

SCALAR(0x811d1bc)
3.14159265

You can assign values to several scalar variables by surrounding
variables and values in parentheses and separating them by commas,
thus making lists:

($one, $two, $three) = ( 1, 2, 3);

There are several
assignment operators besides
= that are shorthand for longer expressions. For
instance, $a += $b is equivalent to $a =
$a + $b. Table A-1 is a complete list.