Was Punic a sister of Hebrew? Cousin? Lost neighbor? Punic prose preserved in Plautus's play.

A comedy written by the Latin playwright Plautus (254-184 BCE) called Poenulus survives. The title means something like "Little Punic Guy."

The Punics were a people who dwelled in Carthage (קרת חדשת), North Africa who originated in Pheonicia (Northern Canaan). References to מדינת אפריקי, "the country" (or people, or language) "of Afriqi" in the Talmud usually* refers to them, but the Talmud also calls the place קרטיגני--Carthage. As former Canaanites, they spoke Punic, that is, a dialect of Semitic that is cognate with Hebrew and the other Semitic languages. Their leaders were called ΣΠΘΜ; שופטים; perhaps pronounced suphethim. The name of the most famous Punic, Hannibal, is something like חן בעל (with the case ending). The language may have survived as late as Augustine (5th century CE, North Africa) who writes that he translates his Punic sayings into Latin so that a wider audience could understand them. A theory has it that Punic never truly died, but evolved into the North African Maghrebi dialect of Arabic, but I don't know about that. In addition, their writing system was awfully close to what I prefer to call the paleo-Hebrew (naturally). So if you could read the one, you could basically read the other.

The play. So, in Poenulus the Punic character Hanno delivers ten lines--in Punic (Act V).

They are:

1 Yth alonim ualonuth sicorathi symacom syth
2 chy mlachthi in ythmum ysthyalm ych-ibarcu mysehi
3 li pho caneth yth bynuthi uad edin byn ui
4 bymarob syllohom alonim ubymysyrthohom
5 byth limmoth ynnocho thuulech-antidamas chon
6 ys sidobrim chi fel yth chyl is chon chen liful
7 yth binim ys dybur ch-innocho-tnu agorastocles
8 yth emanethi hy chirs aelichot sithi nasot
9 bynu yid ch-illuch ily gubulim lasibithim
10 bodi aly thera ynnynu yslym min cho-th iusim

What does this mean? Well, the first line reads thus (as reconstructed by Cyrus H. Gordon):

syth symacom sicorathi ualonuth alonim yth
את אלונים ואלונות זכרתי שמקום זאת
"I call to mind the gods and goddesses of this place."

the sixth:

liful chen chon is chyl yth fel chi sidobrim ys
יש שדוברים כי פעל את כל אש כָּן כֵּן לפעל
"there are those who say that he has done all what was right to do"

As for Hanno, his full name is Anno byn mytthymballe, that is חנא בן מַתַּנבעל.

Finally, at one point Hanno greets with the word "avo," that is חַוֹו! "Live!"

You figure out the rest.

*I only say usually since I have heard that in at least one case Afriqi might refer to a place in the land of Israel rather than Carthage (but named after Carthage). But certainly in the famous Gemara about the lawsuit brought before Alexander the Great by people of Afriqi it refers to Carthaginians:

BT Sanhedrin 91a

ת"ר בעשרים וארבעה בניסן איתנטילו דימוסנאי מיהודה ומירושלים כשבאו בני אפריקיא לדון עם ישראל לפני אלכסנדרוס מוקדון אמרו לו ארץ כנען שלנו היא דכתיב (במדבר לד) ארץ כנען לגבולותיה וכנען אבוהון דהנהו אינשי הוה אמר להו גביהא בן פסיסא לחכמים תנו לי רשות ואלך ואדון עמהן לפני אלכסנדרוס מוקדון אם ינצחוני אמרו הדיוט שבנו נצחתם ואם אני אנצח אותם אמרו להם תורת משה נצחתכם נתנו לו רשות והלך ודן עמהם אמר להם מהיכן אתם מביאים ראייה אמרו לו מן התורה אמר להן אף אני לא אביא לכם ראייה אלא מן התורה שנאמר (בראשית ט) ויאמר ארור כנען עבד עבדים יהיה לאחיו עבד שקנה נכסים עבד למי ונכסים למי ולא עוד אלא שהרי כמה שנים שלא עבדתונו אמר להם אלכסנדרוס מלכא החזירו לו תשובה אמרו לו תנו לנו זמן שלשה ימים נתן להם זמן בדקו ולא מצאו תשובה מיד ברחו והניחו שדותיהן כשהן זרועות וכרמיהן כשהן נטועות ואותה שנה שביעית היתה

Our Rabbis taught: On the twenty-fourth of Nisan the revenue farmers were removed from Judah and Jerusalem. For when the Africans came to plead against the Jews before Alexander of Macedon, they said, 'Canaan belongs to us, as it is written, The land of Canaan with the coasts thereof; and Canaan was the ancestor of these people [i.e., ourselves].' Thereupon Gebiha b. Pesisa said to the Sages, 'Authorise me to go and plead against them before Alexander of Macedon: should they defeat me, then say, "ye have defeated but an ignorant man of us;" whilst if I defeat them, then say to them thus: "The Law of Moses has defeated you." 'So they authorised him, and he went and pleaded against them. 'Whence do ye adduce your proof?' asked he. 'From the Torah,' they replied. 'I too,' said he, 'will bring you proof only from the Torah, for it is written, And he said, Cursed be Canaan; a servant of servants shall he be unto his brethren. Now if a slave acquires property, to whom does he belong, and whose is the property? Moreover, it is now many years that ye have not served us.' Then Alexander said to them, 'Answer him!' 'Give us three days' time,' they pleaded. So he gave them a respite; they sought but found no answer. Immediately thereon they fled, leaving behind their sown fields and their planted vineyards. And that year was a Sabbatical year.