One liners make me nervous, so here is a way to get at all the html files in a directory, works on windows with ActiveState, maybe works on unix as well... hope this helps!

#use strict;
#use warnings;

my ($dirname, $file, %words);

opendir(DIR, ".") or die "can't opendir $dirname: $!";

while (defined($file = readdir(DIR))) {
    if ($file =~ /\.html?/) {
        open my $F, $file or die "Could not open $file\n";
        while (<$F>) {
        #do stuff
        s/
            (?<=                  # Look back-group
             weak                # Match the word weak
             <INPUT TYPE=radio NAME=     # tag
             (                   # Capuring group: $1 / \1
               \w{2}\d\w{2}      # 
             )                   # End-capture
             VALUE=\d>           # tag
         
             (?:                 # Non capturing group
               <INPUT TYPE=radio NAME=     # tag
               \1                # It's possible that this should be $
+1, as I said, the code is untested.
               VALUE=\d>
             ){6}                # There are 7 input tags, one already
+ matches, so 6 to go.
             )                   # End look-back
             (?=                 # Look-ahead-group
               strong
             )                   # End look-ahead
           /
             the text you want to insert
           /ixg;
        }
        close $F;
        }
}
closedir(DIR);
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UPDATE: Integrated holli's fix and animator's regex code from below. (untested!)