Mastering Perl for Bioinformatics [Electronic resources] نسخه متنی

A.11 Basic Operators

For more information on how operators work, consult the
perlop
documentation bundled with Perl.

A.11.1 Arithmetic Operators

Perl has the basic five
arithmetic operators:

+

Addition

-

Subtraction

*

Multiplication

/

Division

**

Exponentiation

These operators work on both integers and floating-point values (and
if you're not careful, strings as well).

Perl also has a modulus operator, which computes
the remainder of two integers:

% modulus

For example, 17 % 3 is 2, because 2 is left over
when you divide 3 into 17.

Perl also has autoincrement and
autodecrement operators:

++ add one
-- subtract one

Unlike the previous six operators, these change a
variable's value. $x++ adds one
to $x, changing 4 to 5 (or a to b).

A.11.2 Bitwise Operators

All
scalars, whether numbers or strings,
are represented as sequences of individual bits
"under the hood." Every once in a
while, you need to manipulate those bits, and Perl provides five
operators to help:

&

Bitwise and

|

Bitwise or

^

Bitwise xor

>>

Right shift

<<

Left shift

A.11.3 String Operators

Two strings
may be concatenated, i.e., joined end to end, with the dot operator:

'This is a ' . 'joined string'

This results in the value 'This
is a joined
string'.

A string may be repeated with the x operator:

print "Hear ye! " x 3;

This prints:

Hear ye! Hear ye! Hear ye!

A.11.4 File Test Operators

File test operators are unary operators that
test files for certain characteristics, such as -e
$file, which returns true if the file
$file exists. Table A-2 lists
some available file test operators.