That is a cool story. I can well believe it. I’ve seen those machetes, made in a similar way. Our yard guys would use them to literally cut the grass with them and most anything else. We called them “parangs”. I have since learned and value machetes as wonderful outdoor tools. I own three machetes here in the states and several at our home overseas.
As to monitors, the local name for them is “kaki empat”, meaning “four legs”. Every now and again, one would start through the yard. Their journeys were never completed. My dingo would spot them and grab those things right behind its head and start whipping them around. Soon, the tail would fly off and the neck would break and that would be that. The dog was never bitten. That dingo was a great dog. Bad things, both animal and human would leave us alone while he was alive. I miss that dog.
It sounds like you are describing geckos, which are larger than the usual ones you see around lights, but smaller than the monitor lizards. (Geckos can be between six inches and a foot long...with tail IIRC) I say this because I am sure monitors don’t lose their tails...but geckos do.
But geckos are nothing to sneeze at either. I got bit by a good sized one trying to capture it, and the only way I got it to let go was be squeezing it so forcefully being its head that I recall its jaw and head nearly became misshapen before it opened its mouth...I had two little neat rows of blood droplets from those little needle-like teeth!
I had to look up the parang...the ones we had were very plain compared to that...I sure would have liked to have one of those...:
I have an old Army-issue type of machete, but the thing is worthless for any more than self defense (I would guess) since it has no heft or weight to it, and doesn’t seem to hold much of an edge...it is kind of flimsy. So...I keep it near my garage door in case I ever need it.
The heavier one I had as a kid could cut down a six inch bamboo with no problem. I suspect this one I have would require repeated hacking...