Perl has an operator that does what you're asking for. It's the diamond operator, and when used 'empty', it reads each item listed in @ARGV sequentially. See perlop. Here's a snippet from the documentation:

The null filehandle <> is special: it can be used to emulate the behavior of sed and awk. Input from <> comes either from standard input, or from each file listed on the command line. Here's how it works: the first time <> is evaluated, the @ARGV array is checked, and if it is empty, $ARGV[0] is set to "-", which when opened gives you standard input. The @ARGV array is then processed as a list of filenames. The loop

    while (<>) {
    ... # code for each line
    }
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is equivalent to the following Perl-like pseudo code:

    unshift(@ARGV, '-') unless @ARGV;
    while ($ARGV = shift) {
        open(ARGV, $ARGV);
        while (<ARGV>) {
            ... # code for each line
        }
    }
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