These types of documents are not going to change academic understanding of the First World War but they have immense value in understanding the individual experiences of soldiers who fought in the conflict. I don't know the current state of Italian First World War academia but I know that in English speaking countries, the academia has shifted largely to better understanding the individual experiences of the men and women who served in the conflict. The poem/song lyric likely embodies the emotions that that soldier felt about the war whether they patriotic feelings, that he was doing his duty for his country or to protect his family. Perhaps they reveal the despondency he was feeling about the losses her was seeing, the destructive capability of industrial war.

These types of documents along with letters, journals, diaries are what we have to understand the mindsets of the past and that makes them invaluable and irreplaceable. I'm sure you would be able to find a local historian who has interests in the region's history or a local war historians focused on individuals from the region who enlisted or were conscripted. I'd start with your local historical society. Where I come from, every town has some sort of history group that specialises in the area they are based. Finding a group that specialises in the area that the soldier came from would be the best starting point. They might also be able to advise on how to best preserve the document.

I want to emphasice what u/TheWellSpokenMan said - personal documents and especially poems, songs or plays, regularly turn out to be treasures for historians, as they can be used to look through a window behind the curtain of oral history (told by relatives etc.) or their later drafted biographies. They often depcit a very unique take on situations, relations, emotions etc. of soldiers in combat.

You should definetly reach out to a local museum - there's a very high chance they'd be thankful for the source.