Here's a version that approximates your desired usage without gotos or source filters, and it's not obfuscated, IMO. Each yield section gets its own sub, and they're all wrapped in a sub that sets up the variables for the coroutine scope.
use warnings;
use strict;
package Coroutine;
sub prototype {
my $class = shift;
bless shift(), $class;
}
sub instance {
my $self = shift;
my @sections = $self->(@_);
return sub {
return () unless @sections;
(shift @sections)->(@_);
}
}
package main;
my $coroutine = Coroutine->prototype(
sub {
my $foo = shift;
my @bar = @_;
(
sub {
print "1st section:\n";
print " $_\n" for @bar;
return $foo++;
},
sub {
print "2nd section:\n";
print " $foo\n";
return rand() > .5 ? 'weird' : ++$foo;
},
sub {
print "3rd section:\n";
print " The end is near - goodbye cruel ";
return pop @bar;
}
)
}
);
my $wacky = $coroutine->instance(42, 'hello', 'world');
print "returned($_)\n" while ($_ = $wacky->());
print "Resetting...\n";
$wacky = $coroutine->instance('another', 'time', 'through');
print "returned($_)\n" while ($_ = $wacky->());
__END__
1st section:
hello
world
returned(42)
2nd section:
43
returned(44)
3rd section:
The end is near - goodbye cruel returned(world)
Resetting...
1st section:
time
through
returned(another)
2nd section:
anothes
returned(anothet)
3rd section:
The end is near - goodbye cruel returned(through)
Caution: Contents may have been coded under pressure.