Question

Consider the following silly Perl program:

$firstarg = $ARGV[0];

print $firstarg;

$input = <>;

print $input;

I run it from a terminal like:

perl myprog.pl sample_argument

And get this error:

Can't open sample_argument: No such file or directory at myprog.pl line 5.

Any ideas why this is? When it gets to the <> is it trying to read from the (non-existent) file, “sample_argument” or something? And why?

Answer 1

<> is shorthand for “read from the files specified in @ARGV, or if @ARGV is empty, then read from STDIN“. In your program, @ARGV contains the value ("sample_argument"), and so Perl tries to read from that file when you use the <> operator.

You can fix it by clearing @ARGV before you get to the <> line:

$firstarg = shift @ARGV;
print $firstarg;
$input = <>;       # now @ARGV is empty, so read from STDIN
print $input;