if statement perl, how to identify my chosen value

i want to write down in perl a code which should mean: if a>0 or b>0 or c>0, pick up the lowest value among those three and do stuff. I am ok with the first part, which i coded

if(a>=0 || b>=0 || c>=0) { #but here i don't know how to pick up the lowest value}

could you please help me out? thanks a lot Alfredo