Perl Logical Operators

Perl has two kind of logical operators: pure operators and keywords. Some share the same function but with different precedence when interpreted by Perl. The following table shows their function and similarity.

Generally, keywords have lower precedence to both the pure operators and the assignment operator (=), whereas pure operators have higher precedence over the assignment operator. Therefore, a typical use of a keyword logical operator is to use it as a method to control flow, rather than used together with an assignment operator which could be confusing.

open (my $fileHandle, $fileName)
  or die "can't open the file $fileName"  # if fail, print out
                                          # the error message

my $wrongNumber = 0 or 1  # expected to be 1, but resulted in 0
                          # because `or` has lower precedence than `=`

If an assignment operator is involved, use pure logical operators instead of keywords.