To force perl to perform an operation of lower precedence first, use brackets

   

#!/usr/bin/perl

use warnings;
print(3 + 7) * 15;

1.	Demonstrates the difference between pre- and postincrement
2.	Adding a number and a string
3.	You can combine operators such as +, -, and * with the assignment operator
4.	Power with **
5.	Minus power
6.	Float power
7.	Left shift
8.	After incrementing
9.	After pre-increment: ++$a * 2
10.	After pre-decrement
11.	Using auto-increment operator for a string with digits
12.	Using auto-increment operator for a string
13.	A program that uses the pre-increment operation.
14.	Post-increment operation.
15.	Operators demo: Arithmetic Operators
16.	Precedence and Associativity
17.	Add 3 to $var; same as $var=$var+3
18.	Subtract 1 from $var
19.	Square $var
20.	Modulus operator
21.	Arithmetic Operators in action
22.	Autoincrement and Autodecrement Operators and Assignment
23.	Numeric Operators
24.	Use parentheses wherever possible to force precedence.
25.	Remainder and power
26.	An example of exponentiation
27.	%, the remainder, or 'modulo' operator
28.	The autoincrement operator
29.	Basic Numeric Operations
30.	Increment and Decrement Operations
31.	Increment and Decrement Operators
32.	Basic arithmetic operators.
33.	Built-in Perl Arithmetic Functions
34.	Pre-increment string value

To force perl to perform an operation of lower precedence first, use brackets : Arithmetic Operators « Language Basics « Perl