from the documentation:

    use GRID::Machine qw(is_operative);
    use Data::Dumper;

    my $machine = GRID::Machine->new(host => 'user@remote.machine.doma
+in');

    my $p = { name => 'Peter', familyname => [ 'Smith', 'Garcia'], age
+ => 31 };

    print Dumper($machine->eval(q{
      my $q = shift;

      $q->{familyname}

      }, $p
    ));
[download]

Notice how it pulls in the $p hashref of variables, so your code would be code something like:

my $p = { a => 10 };
print Dumper( $machine->eval(q{
  my $q = shift;
  print $q->{a}."Value of A\n"; # It's not working
  sample->function($q->{a});
}, $p));
[download]