>>189
Watashi ga Kita Watashi ga Kita
↓
Watashi(=Yamada) ga Kita Watashi(=Yamada) ga Kita
↓
Watashi(=Yamada)(=Yamada) ga Kita Watashi(=Yamada)(=Yamada) ga Kita
↓
Watashi(=Yamada)(=Yamada)(=Yamada) ga Kita Watashi(=Yamada)(=Yamada)(=Yamada) ga Kita


$string =~ /Watashi$s/igo