Why does perl take a file name provided on the command line and open it for use with standard input? How should I prevent that?

I'm working on a program that takes a couple of files as command line arguments. At some point in the program, I want to prompt the user for an action to take.

The lines that accept the user's response look something like this:

print "Remove '$origin'? ([Y]es, [N], A(ll), ne[V]er; default: N) ";
my $answer = <>;
print "answer: |$answer|\n" if (DEBUG);
chomp($answer);
$answer = lc($answer);
if ($answer eq ('y' or 'yes')) {
    unlink $origin;
}
[download]

The problem is that <> is filled with the content of the first file on the command line. This is entirely unexpected. Why would the file be opened at all? I would have expected that filename to be treated only as a scalar value.

I confirmed this by adding while (<>) { print; } before I prompted for an answer.

To double-check, and eliminate problems caused by modules or other code, I put that line into a separate script and got the same results:

#!/usr/bin/perl -w
use strict;
while (<>) { print; }
[download]

Thank you.

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