Perl in a Nutshell, 2nd Edition

Numbers

Perl stores numbers internally as either signed integers or double-precision, floating-point values. Numeric literals are specified by any of the following floating-point or integer formats:

12345

Integer

-54321

Negative integer

12345.67

Floating point

6.02E23

Scientific notation

0xffff

Hexadecimal

0377

Octal

4_294_967_296

Underline for legibility

Since Perl uses the comma as a list separator, you cannot use a comma for improving the legibility of a large number. To improve legibility, Perl allows you to use an underscore character instead. The underscore works only within literal numbers specified in your program, not in strings functioning as numbers or in data read from somewhere else. Similarly, the leading 0x for hex and 0 for octal work only for literals. The automatic conversion of a string to a number does not recognize these prefixes—you must do an explicit conversion.

Be aware that in Perl 5.8, there are many changes in how Perl deals with integers and floating-point numbers. Regardless of how your system handles numbers and conversion between characters and numbers, Perl 5.8 works around system deficiencies to force more accurate number handling. Furthermore, whereas prior to 5.8 Perl used floating-point numbers exclusively in math operations, Perl 5.8 now uses and stores integers in numeric conversions and in arithmetic operations.