ものがある and verbs ending in らぁ instead of る


I was reading a manga and came across this line:

> 時代はもう侍なんざ必要としてねェがよ  
>  どんなに時代が変わろうと  
>  **人には忘れちゃならねーもんがあらぁ**

Which is roughly translated to:

> The time has come where samurais are no longer needed, but no matter how the
> times may change, ...

I can understand the first two parts (but if there are any errors in my
translation, please let me know), what I'm having problems with is the last
part in bold. I have two questions.

First is, what does あらぁ mean? Why is it not ある? I tried looking for sentences
with similar らぁendings and found some
[here](https://ejje.weblio.jp/sentence/content/%22%E3%82%89%E3%81%81%22). I'll
just copy-paste some sentences and their translations from the website below:

> おまえを男にしてや **らぁ** 、ジム。  
>  I'll make a man of you, Jim.

> あと勇気があ **らぁ** 、ライオンでさえロング・ジョンにはかなわんぞ！  
>  and brave--a lion's nothing alongside of Long John!

> いいか、やつとうまいことやりさえすりゃあ、やつは時計がらみのことなら、ほとんどなんでも塩梅してくれ **らぁ** ね。  
>  Now, if you only kept on good terms with him, he'd do almost anything you
> liked with the clock.

_Edited:_ Realized I was taking lines from Japanese versions of English books,
so I added some actual Japanese examples below:

> 犬にだってプライドがあ **らぁ** な  
>  Even dogs have their pride (source: title of [this
> post](http://blog.livedoor.jp/sith_ko2/archives/51133162.html))

> PCいらずのキャプチャーマシン  
>  GV-HDRECを注文した これでPS2でも録画でき **らぁ**  
>  Video capture device without a PC. Just ordered a GV-HDREC. With this it is
> possible to record even on a PS2. (source:
> [tweet](https://twitter.com/rurarbou_new/status/1439857818182447104))

From what I understand, there don't seem to be any differences from the る
ending of the verbs. Is らぁ supposed to be some sort of speech style or
dialect?

My second question is about the grammar structure of the last part. I found
online sources which state that AにはBものがある is a structure which means A gives
off feeling B, or in A there exists some element/feature B. Is that grammar
used in my above sentence, or is it something else? If so, does the に function
as a particle which points to the place where something exists, is it a pair
with the がある part? Can the last sentence be translated as " _Within the
people('s hearts?), there are things they must never forget_ "?




It looks like らぁ in your examples denotes quickly pronounced/slurred るわ:

人には忘れちゃならねーもんがあらぁ → 人には忘れちゃならねーもんがあるわ

おまえを男にしてやらぁ、ジム。→ おまえを男にしてやるわ、ジム。

あと勇気があらぁ → あと勇気があるわ(or possibly あと勇気があるな)

ほとんどなんでも塩梅してくれらぁね。→ ほとんどなんでも塩梅してくれるわね。

これでPS2でも録画できらぁ → これでPS2でも録画できるわ

Going by the Stevenson’s quotes on Weblio, it seems to be used for “rough men”
speech.

Originally it may have come from the characteristic Tokyo Shitamachi
pronunciation; see [What does the 「たあ」 do in this
sentence?](https://japanese.stackexchange.com/q/32933)

