use strict;

{
  package Foo;
  my $str = 'foo str';
  sub str {
    my $class = shift;
    $str = $_[0] if @_;
    return $str;
  }
}

{
  package Bar;
  my $str = 'bar str';
  sub str {
    my $class = shift;
    $str = $_[0] if @_;
    return $str;
  }
}

my $class = 'Foo';
my $value = $class->str();