# this is bad...
#
sub do_something {
   if ( $MyApp::VERSION < 1.0 ) {  # a global
      do_something_simple();
   }
   else {
      do_something_complex();
   }
}

do_something();

# this is good...
#
sub do_something {
   my ($version) = @_;
   if ( $version < 1.0 ) {  # a local variable
      do_something_simple();
   }
   else {
      do_something_complex();
   }
}

do_something(1.2);