while (<*.c>) {
        chmod 0644, $_;
    }

is equivalent to

    open(FOO, "echo *.c | tr -s ' \t\r\f' '\\012\\012\\012\\012'|");
    while (<FOO>) {
        chop;
        chmod 0644, $_;
    }

In fact, it's currently implemented that way.  (Which
means it will not work on filenames with spaces in them
unless you have csh(1) on your machine.)