Perl Operators

Arithmetic Operators

These are used to perform mathematical calculations on numbers. However, they are NOT used to combine strings as there are some special string operators for this. They are :

Operator	Function
+	Addition
-	Subtraction, Negative Numbers, Unary Negation
*	Multiplication
/	Division
%	Modulus
**	Exponent

To use these, you will place them in your statements like a mathematical expression, with or without the space used only to make it more readable. So, to say add two variables into a third variable, you could write something like this :

code:

$revenue = 20;
$sales   = 10;
$total   = $revenue + $sales;
print "Sales $sales, plus other revenue $revenue, equals total $total\n";

output:

Sales 10, plus other revenue 20, equals total 30

As can be seen, it is quite similar to other programming languages.

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Assignment Operators

Above we have already seen the use of the equal sign, = assignment operator. Here is a list :

Operator	Function
=	Normal Assignment
+=	Add and Assign
-=	Subtract and Assign
*=	Multiply and Assign
/=	Divide and Assign
%=	Modulus and Assign
**=	Exponent and Assign

Bit Assignment and Testing

It is often 'tidier' to use BITS in a flag...

Operator	Function
$f \|= $BIT;	OR in $BIT value
$f &= ~$BIT;	AND out $BIT value
if ($f & $BIT) {...}	Test $BIT value
$BIT = $BIT >> 1	Shift $BIT value right 1 place
$BIT = $BIT << 2;	Shift $BIT value left 2 places

code:

#!/usr/bin/perl
use strict;
use warnings;
my $F_HADMEM = 8;
my $flag = 1;
my $msg = '';
$msg = ($flag & $F_HADMEM) ? "Got HADMEM" : "No HADMEM";
print "Value of flag = $flag ($msg)\n";
$flag |= $F_HADMEM;  # ADD the BIT to flag
$msg = ($flag & $F_HADMEM) ? "Got HADMEM" : "No HADMEM";
print "Value of flag = $flag ($msg)\n";
$flag &= ~$F_HADMEM; # REMOVE the BIT from the flag
$msg = ($flag & $F_HADMEM) ? "Got HADMEM" : "No HADMEM";
print "Value of flag = $flag ($msg)\n";
$flag = 1;
my $wrap = 0;
while ($flag) {
    print "$flag ";
    $flag = $flag << 1; # shift bit(s) to left, 1 position
    $wrap++;
    if ($wrap > 7) {
        print "\n";
        $wrap = 0;
    }
}
print "\n" if ($wrap);

output:

Value of flag = 1 (No HADMEM)
Value of flag = 9 (Got HADMEM)
Value of flag = 1 (No HADMEM)
1 2 4 8 16 32 64 128
256 512 1024 2048 4096 8192 16384 32768
65536 131072 262144 524288 1048576 2097152 4194304 8388608
16777216 33554432 67108864 134217728 268435456 536870912 1073741824 2147483648

As can be seen, it is quite similar to other programming languages.

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Increment/Decrement

While a variable can be increased or decreased by 1 by using :-

$variable = $variable + 1;
$value    = $value - 1;

the '++' or '--' operators can also be used, respectively.

Operator	Function
++	Increment (Add 1)
--	Decrement (Subtract 1)

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Numeric Comparison

For numeric values, the following can be used in a comparison. Note, this is for numeric values only. Strings have their own comparison operators. :

Operator	Function
==	Equal to
!=	Not Equal to
>	Greater than
<	Less than
>=	Greater than or Equal to
<=	Less than or Equal to

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Adding Strings - concatenation

Note it is NOT a '+', but a full stop, '.', that joins strings together, like :

Operator	Function
.	Concatenate Strings
.=	Concatenate and Assign

For example :-

code:

$firstname = 'John'; # assignment
$lastname  = 'Doe';  # assignment
print "He is called ".$firstname." ".$lastname."\n"; # output concatenation

output:

He is called John Doe

Or :-

code:

$name = 'John'; # assignment
$name .= ' ';   # concatenation and assign
$name .= 'Doe'; # concatenation and assign
print "He is called $name.\n";

output:

He is called John Doe.

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String Comparison

Operator	Function
eq	Equal to
ne	Not Equal to
gt	Greater than
lt	Less than
ge	Greater than or Equal to
le	Less than or Equal to

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Logical Operators

Operator	Function
&&	AND
\|\|	OR
!	NOT

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EOF - perl_ops.htm

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