my $saved = $magical; 
... 
$magical = ...;
 ... 
$magical = $saved

##</code><code>##

sub dont_mess_pos { 
  my $vr=\$_[0]; 
  my $pos=pos($$vr); 
  my $s=$$vr; 
  $_[0]=42; 
  $$vr=$s;
  pos($$vr)=$pos 
}

##</code><code>##

  DB<80> my $a="xxx";scalar ($a=~/x/g);print pos($a); tst $a; print $a,pos($a)
1xxx1