Semantics : LinesStatement
This opens an input text stream and read the lines; each line is stored in
the built-in variable $_ for program to process. The input stream can be an
open file, a file name, a URL or a file in a zip archive. The text encoding can
be specified in < and > . The for clause is for filtering the lines.
It is a boolean expression typically involving $_ , such as
$_.isNotEmpty()
.