13.1. File test or -X operators

Before we try to read from a file or try to write to a file
we might want to check our rights, if we can do the required action at all.

For this there is a bunch of so called -X operators. Usually you use them in 
an if statement:

if (-e "file.txt") {
    print "File exists !\n";
}

• -e File (or directory) exists

• -r File (or directory) is readable by this user

• -w File (or directory) is writable by this user

• -x File (or directory) is executable by this user

• -d Entry is a directory

• -l Entry is a symbolic link

• -s Size of the file (hence also means 'file is not empty')

• -M Number of days between the modification date of a file and the start time of our script

Hence -s can be used either in an if statement or like this:

$size = -s $filename;

There are more such operators see perldoc -f -x