• Access to files is similar to shell redirection
• open allows access to the file
• Redirect characters (<, >) define access type
• Can read, write, append, read & write, etc.
• Filehandle refers to opened file
• close stops access to the file
• $! contains IO error messages
• perldoc perlopentut has complete description

         open INPUT,  "<  datafile" or die "Can't open input file: $!";
         open OUTPUT, ">  outfile " or die "Can't open output file: $!";
         open LOG,    ">> logfile " or die "Can't open log file: $!";
         open RWFILE, "+< myfile  " or die "Can't open file: $!";

         close INPUT;