# This code is not tested. Sorry.
sub _find_var_loop {
  my($hash,$prefix,$var) = @_;
  my @results;
  # go through each entry in our symbol table hash...
  while (my($name,$glob) = each %$hash ) {
    if ($var eq \${ $glob }) {
      push @results, $perfix.$var; # add $var to our list
    }

    # is it another symbol table hash?
    # (ignore main:: to not infinite loop)
    if ($name =~ /::\z/ and $name ne 'main::') { 
      # recurse...
      push @results, 
             _find_var_loop(\%{ $glob }, $prefix.$name, $var);
    }
  }
  return @results;
}

sub find_var { # usage: my @names = find_var($var);
  return _find_var_loop(\%main::, "", \$_[0])
}