List Operators (Rightward)
On the right side of a list operator, the comma has very low precedence, such that it controls all comma-separated expressions found there. The only operators with lower precedence are the logical operators "and" , "or" , and "not" , which may be used to evaluate calls to list operators without the need for parentheses:
open HANDLE, "< :utf8", "filename" or die "Can't open: $!\n";
However, some people find that code harder to read than writing it with parentheses