You don't have to create a separate sub. Alternatives:
my $sub = sub { my ($str) = @_; sub { $str } }->($str);
my $sub = sub { my $str = $str; sub { $str } }->();
my $sub = do { my $str = $str; sub { $str } };
my $str_copy = $str;
my $sub = sub { $str_copy };
In practice, it's usually a non-issue since you either have a variable that doesn't change to begin with
for my $str (...) {
... sub { ... $str ... } ...
}
or you want to factor out the code to a sub anyway.
sub make_list_iterator {
my @list = @_;
return sub {
return @list ? shift(@list) : ();
};
}
my $iter = make_list_iterator(@list);