Perl Language Variables Scalars
Example
Scalars are Perl's most basic data type. They're marked with the sigil $ and hold a single value of one of three types:
- a number (
3,42,3.141, etc.) - a string (
'hi',"abc", etc.) - a reference to a variable (see other examples).
my $integer = 3; # number
my $string = "Hello World"; # string
my $reference = \$string; # reference to $string
Perl converts between numbers and strings on the fly, based on what a particular operator expects.
my $number = '41'; # string '41'
my $meaning = $number + 1; # number 42
my $sadness = '20 apples'; # string '20 apples'
my $danger = $sadness * 2; # number '40', raises warning
When converting a string into a number, Perl takes as many digits from the front of a string as it can – hence why 20 apples is converted into 20 in the last line.
Based on whether you want to treat the contents of a scalar as a string or a number, you need to use different operators. Do not mix them.
# String comparison # Number comparison
'Potato' eq 'Potato'; 42 == 42;
'Potato' ne 'Pomato'; 42 != 24;
'Camel' lt 'Potato'; 41 < 42;
'Zombie' gt 'Potato'; 43 > 42;
# String concatenation # Number summation
'Banana' . 'phone'; 23 + 19;
# String repetition # Number multiplication
'nan' x 3; 6 * 7;
Attempting to use string operations on numbers will not raise warnings; attempting to use number operations on non-numeric strings will. Do be aware that some non-digit strings such as 'inf', 'nan', '0 but true' count as numbers.
