use strict;
use warnings;

{
  package TiedObject;

  sub TIESCALAR {
    my $sClass = shift;
    return bless([ @_ ], $sClass);
  }
  sub STORE {}
  sub FETCH { shift->[0]; }
}

my $sErr;
tie $sErr, 'TiedObject', 5, "More data";
printTiedObject($sErr);

sub printTiedObject {
  my $oErr = tied($_[0]);

  #does not copy scalar, prints out "...is tied to..."
  print "using \@_ directly\n";
  if (defined($oErr)) {
    print "\$_[0] is tied to <$oErr>\n";
  } else {
    print "\$_[0] is not tied";
  }

  #copies scalar, prints out "..is not tied"
  print "\nafter \$param0 = shift \@_\n";
  my $param0 = shift @_;
  $oErr = tied ($param0);
  if (defined($oErr)) {
    print "\$param0 is tied to <$oErr>\n";
  } else {
    print "\$param0 is not tied\n";
  }
}

##</code><code>##

using @_ directly
$_[0] is tied to <TiedObject=ARRAY(0x814ed48)>

after $param0 = shift @_
$param0 is not tied