How can I use macros in Perl?

Question

How do I use macros in Perl, like I do in C?

Example:

#define value 100 
print value; 

I want to get the output as 100.

Answer 1

If you just want to define constants (like your example) rather than full macros, there are a couple of perl ways to do this.

Some people like:

use constant value => 100;
print value;

Note that 'value' is a subroutine, not a 'variable'. This means you cannot interpolate it in strings so you have to do. print "The value is ".value."\n";.

The "Best Practices" crowd like:

use Readonly;
Readonly my $value => 100;
print $value;

However, unlike constant, Readonly is not part of the core perl distribution and so needs to be installed from CPAN.