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Perl boolean

Explains boolean in Perl.

False values

There are five false values in Perl. Undefined value, equal to 0 as number, empty string, string "0", a empty list are false value.

1	undef	Undefined value
2	""	Empty string
3	0	Equal to 0 as a number.
4	"0"	String 0
5	()	Empty list

True values

The true value in Perl is all values except the above.

The following is the example of true values.

# 1
1;

# String
"Hellow"

# object
my $obj = Point->new;

# String "0.0"
"0.0"

Note that "0.0" is a true value. Only "0" is a false value in strings which has more than zero length.

Example program

This is an example boolean value.

# Boolean example
my $var; # False. The variable immediately after definition is undef
$var = undef; # False.

$var = 0; # False.
# $var = 0.0 A number equivalent to 0 is false.
$var = 1; # True.

$var = ''; # False
$var = '0'; # False.
# $var = '0.0' True. True for strings except '0' and''.

See the following article for the combination with if statement.

• Conditional branching by if statement