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:











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.

Table A-2. File test operators




File is readable


File is writable


File is executable


File is owned by "you"


File exists


File has zero size in bytes


File has nonzero size (returns size in bytes)


File is a plain file


File is a directory (a.k.a. folder)


File is a symbolic link


Filehandle is opened to a terminal


File is a text file


File is a binary file


Age of file (at startup of program) in days since modification


Age of file (at startup of program) in days since last access


Age of file (at startup of program) in days since last inode change