my $foo = defined($some_hash{bar}) and $some_hash{bar};

##</code><code>##

( my $foo = defined($some_hash{bar}) ) and $some_hash{bar};

##</code><code>##

my $foo = defined($some_hash{bar}) && $some_hash{bar};

##</code><code>##

my $foo = ( defined($some_hash{bar}) and $some_hash{bar} );