That has some caveats. First, you shouldn't use a glob as an argument to that for security reasons. Also, that will create backup files named with .bak, just in case you make a mistake. Finally, if that string appears more than once and you want all instances lowercased, add a /g to the substitution.

-sauoq
"My two cents aren't worth a dime.";

This can be done from the command line:

perl -p -i.bak -e 's:CLASSATTRIBUTES:classattributes:g' *
[download]

...though I'm not sure whether that's an option for you or not.

Update: Ah yes, please read the excellent comments below. If you're doing this from within a script, this works:

my @files = qw( foobar zoot );

for my $file ( @files ) {
    ## Read the contents of the file
    open FILE, "<$file";
    my $contents; do { local $/; $contents = <FILE>; };
    close FILE;

    ## Make your changes
    $contents =~ s:CLASSATTRIBUTES:classattributes:g;

    ## Write the modified contents back to the file
    open FILE, ">$file";
    print FILE $contents;
    close FILE;
}
[download]

Those who know that they are profound strive for clarity. Those who
would like to seem profound to the crowd strive for obscurity.
            --Friedrich Nietzsche

Don't use a -p and a * like that unless you know what you are doing. See the discussion starting at Dangerous Diamonds! for an explanation.

-sauoq
"My two cents aren't worth a dime.";