$foob{$_} //= '' for keys %foo;

##</code><code>##

$_ //= '' for values %number_of_immortal_perl_monks

##</code><code>##

$number_of_immoral_perl_monks{$_} //= '' for keys %number_of_immortal_perl_monks

##</code><code>##

$foo{$_} //= '' for keys %foo;