Congratulations on a fine choice of programming language ;o)

A few really good habits to start with are:

#!/usr/bin/perl -w 
use strict;
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This takes away the niceness of not having to declare variables, but makes spotting bugs waaaay faster ;)

$addthis=join("", <TEXT>);
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Whoa!! Nice use of join, it makes sense now I think about it. I'd suggest using ' instead of " as " interpolates stuff, and if you don't need it use ' instead ;)

open (FILES,"files.txt") || die "Could not open file: $! \n";
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I prefer: open FOO,'foo.txt' or die "$! foo.txt\n";

Maybe use a while loop or a for loop, as for loops can traverse arrays too.

for (<FILES>){
    chomp; # each item of the array is placed in $_ for the scope of t
+he for
    unless (open (D,$_)){ # no need to wrap the variable in quotes
        print STDERR "$!:$_\n"; # In case the failure to read one file
+ isn't critical
        next; # Skips all the other commands in the loop and goes to t
+he next iteration.
    }
    my $newrecord=$addthis.join('',<D>);
    close(D);
    open (D,">$_") || die "Could not write to: $! \n";
    print "$_\n";
    print D $newrecord;
    close (D)
}
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Watch yourself here, DATA is a reserved word IIRC like:

#!/usr/bin/perl -w
use strict;
$someperl=<DATA>;
__DATA__
Some data
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Now $someperl should contain "Some data".

--

Brother Frankus.

¤