{ 
    my $s = 'the quick brown fox'; 
    sub Body{ 
        ($s) = @_ if @_; 
        $s 
   } 
}
print Body();

the quick brown fox

Body = 'fred';
Can't modify non-lvalue subroutine call in scalar assignment at (eval 3) line 1, at EOF

Body( 'fred' );
print Body();

fred