doubler

#!/Users/brian/bin/perls/perl5.22.0

use v5.22;
use feature qw(signatures);
no warnings qw(experimental::signatures);

package Tie::Scalar::Sub {
	use parent qw(Tie::Scalar);
	use Carp qw(croak);

	sub TIESCALAR ( $class, $code ) {
		croak "You need to give me a code reference"
			unless ref $code eq ref sub {};
		bless { code => $code }, $class;
		}

	sub FETCH ( $self ) { $self->{code}() }

	sub STORE {
		croak "You can't assign to this scalar";
		}
	}

my $sub = sub () {
	state $value = 37;
	state $ratio = 2;

	$value *= $ratio;
	};

tie my $scalar, 'Tie::Scalar::Sub', $sub;

my $count;
while( $count++ < 10 ) {
	say $scalar;
	}

tie-sub.pl

use v5.22;
use feature qw(signatures);
no warnings qw(experimental::signatures);

package Tie::Scalar::Sub {
	use parent qw(Tie::Scalar);
	use Carp qw(croak);

	sub TIESCALAR ( $class, $code ) {
		croak "You need to give me a code reference"
			unless ref $code eq ref sub {};
		bless { code => $code }, $class;
		}

	sub FETCH ( $self ) { $self->{code}() }

	sub STORE {
		croak "You can't assign to this scalar";
		}
	}

my $sub = sub () { 10 + int( 10 * sin( time % 13 ) ) };

tie my $scalar, 'Tie::Scalar::Sub', $sub;

my $count;
while( $count++ < 10 ) {
	sleep 1;
	say $scalar;
	}