$hash{'a'};
print exists $hash{'a'}?'yes':'no';
#no

##</code><code>##

$hash{'a'}=1;
print exists $hash{'a'}?'yes':'no';
#yes

##</code><code>##

$hash{'a'}=$hash{'a'};
print exists $hash{'a'}?'yes':'no';
#yes

##</code><code>##

sub foo{$_[0]}
foo($hash{'a'});
print exists $hash{'a'}?'yes':'no';
#no

##</code><code>##

sub foo{$_[0]=1}
foo($hash{'a'});
print exists $hash{'a'}?'yes':'no';
#yes

##</code><code>##

sub foo{$_[0]=$_[0]}
foo($hash{'a'});
print exists $hash{'a'}?'yes':'no';
#yes

##</code><code>##

sub foo{
	for($_[0]){
	}
}
foo($hash{'a'});
print exists $hash{'a'}?'yes':'no';
#no

##</code><code>##

sub foo{
	for($_[0]){
		$_=1;
	}
}
foo($hash{'a'});
print exists $hash{'a'}?'yes':'no';
#yes

##</code><code>##

for($hash{'a'}){
}
print exists $hash{'a'}?'yes':'no';
#yes

##</code><code>##

sub foo{
	for($_[0]){
		$_=$_;
	}
}
foo($hash{'a'});
print exists $hash{'a'}?'yes':'no';
#no