The <> is a special case of the readline operator. It usually takes a filehandle: <$fh>.
If the filehandle is left out, then the the magic ARGV filehandle is used.
If no command line arguments are given, then ARGV is STDIN. If command line arguments are given, then ARGV will be opened to each of those in turn. This is similar to
# Pseudocode
while ($ARGV = shift @ARGV) {
open ARGV, $ARGV or do{
warn "Can't open $ARGV: $!";
next;
};
while () {
...; # your code
}
}
The $ARGV variable is real, and holds the filename of the file currently opened.
Please be aware that the two-arg form of open (which is probably used here behind the scenes), is quite unsafe. The filename rm -rf * | may not do what you want.
