How to use constants in Perl

#!/usr/bin/perl
	# How to use constants in Perl
	# Best practices include keeping constant's name to be in CAPITALS
	use 5.14.0;
	use warnings;
	#use constant PI => 3.141592653589793238462643383279;
	#use constant TRUE => 1;
	#use constant FALSE => '';
	#Above three lines or below 5 lines both works fine in declaring constants in Perl
	# OR
	use constant {
	PI => 3.141592653589793238462643383279,
	TRUE => 1,
	FALSE => ''
	}; #Do not forget to add ';' at the closing of '}'
	say PI;
	if (TRUE) {
	say 'true';
	} else {
	say 'false';
	}