sub func {
   'b' =~ /(.)/;
   print(@_, "\n");
}

'a' =~ /(.)/;  func($1);    # Prints "b"
'a' =~ /(.)/;  func("$1");  # Prints "a"

##</code><code>##

sub func {
   eval { die "bar\n" };
   print(@_);
}

eval { die "foo\n" };  func($@);    # Prints "bar"
eval { die "foo\n" };  func("$@");  # Prints "foo"