use strict;
use warnings;

package My;
use Data::Dump qw(dump);

my $pkg_sub = __PACKAGE__ . '::A';

my $package_declaration = "package $pkg_sub;";

eval $package_declaration . <<'EndOfPackage';
sub new {
   my $class = shift;
   bless [@_], $class;
}
# some more methods
EndOfPackage

my $new_object = $pkg_sub->new( qw( a b c) );
dump $new_object;

# prints: bless(["a", "b", "c"], "My::A")

1;