use blib;
use Foo;
use Data::Dump qw(dd);
$h = {foo => 1, bar => 2};
while (($k,$v) = each %$h) {
    Foo::foo($h) if $k eq 'foo';
}
dd $h;
__END__
Use of each() on hash after insertion without resetting hash iterator results in undefined behavior, Perl interpreter: 0x224f010 at foo.pl line 6.
{ bar => 2, foo => 1, newkey => "foo" }