ぷる and ﾌﾟﾙ are both "puru". ぷる is written in Hiragana characters, ﾌﾟﾙ is writtern in Katakana characters.

To complicate things further, ﾌﾟﾙ is written in so-called "half-width characters; 半角文字", which are from fiarly legacy code system to represent Japanese characters on computers (I am not an expert on computer history...). Today, so-called "full-width characters; 全角文字", プル, are usually used. However, since it gives a funnier feeling, half-width kana is used for this kind of play.

Maybe that was not your question...