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Beginning Perl for Bioinformatics by James Tisdall

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Basic Operators

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

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 may give you unexpected results if you apply them to 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').

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

String Operators

Two strings may be concatenated—joined together 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 out:

Hear ye! Hear ye! Hear ye!

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

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