BLEU score is being 0

I’m using opennmt-py…
after running the following command it seems something like that:

perl tools/multi-bleu.perl data/Tanzil_bnVal.txt < pred.txt
Use of uninitialized value in division (/) at tools/multi-bleu.perl line 139, line 12.
BLEU = 0.00, 32.2/2.9/0.8/0.0 (BP=0.005, ratio=0.159, hyp_len=149, ref_len=935)

Tanzil_bnVal.txt(bengali language dataset) is my valid dataset and pred.txt is the file that was generated after running