examples/perl/fibonacci-direct.plPerl
#!/usr/bin/perl

use warnings;

my $sqrt5=sqrt(5);
my $phi=(1+$sqrt5)/2;

my $n=shift;
my $f=$phi**$n/$sqrt5;
if($f<int($f)+.5)
{
	$f=int($f);
}
else
{
	$f=1+int($f);
}
print "$f\n";

examples/perl/fibonacci-recurrent.plPerl
#!/usr/bin/perl

use warnings;

my $n=shift;
my ($a, $b)=(0, 1);

($a, $b)=($b, $a+$b) while $n--;
print "$a\n";

examples/perl/fibonacci-recursive.plPerl
#!/usr/bin/perl

use warnings;

sub fibonacci
{
	my $n=shift;
	return $n<2? $n: fibonacci($n-1)+fibonacci($n-2);
}

print fibonacci(shift), "\n";

examples/perl/fibonacci-recursive-memoize.plPerl
#!/usr/bin/perl

use warnings;

my @fibonacci;

sub fibonacci
{
	my $n=shift;
	return $fibonacci[$n] if defined $fibonacci[$n];
	return $fibonacci[$n]=$n<2? $n: fibonacci($n-1)+fibonacci($n-2);
}

print fibonacci(shift), "\n";

examples/perl/fibonacci-matrix.plPerl
#!/usr/bin/perl

use warnings;

sub power
{
	my $n=shift;

	if($n==0)
	{
		return (1, 0, 0, 1);
	}
	elsif($n==1)
	{
		return @_;
	}
	elsif($n % 2)
	{
		my @x=power
			(
				($n-1)/2,
				$_[0]**2+$_[1]*$_[2],
				$_[1]*($_[0]+$_[3]),
				$_[2]*($_[0]+$_[3]),
				$_[1]*$_[2]+$_[3]**2
			);
		return
			(
				$x[0]*$_[0]+$x[1]*$_[2],
				$x[0]*$_[1]+$x[2]*$_[3],
				$x[2]*$_[0]+$x[3]*$_[2],
				$x[2]*$_[1]+$x[3]*$_[3]
			);
	}
	else
	{
		return power
			(
				$n/2,
				$_[0]**2+$_[1]*$_[2],
				$_[1]*($_[0]+$_[3]),
				$_[2]*($_[0]+$_[3]),
				$_[1]*$_[2]+$_[3]**2
			);
	}
}

my $f=(power(shift, 0, 1, 1, 1))[1];
print "$f\n";