opendir(D,$path);
my @perlfiles = grep /\w+\.pl$/, readdir(D); # (or whatever works for you)
closedir D;

for my $file (@perlfiles) {
   my $name = "$path/$file";
   unless (open(P,$name)) {
      warn "what happened to $name? $!";
      next;
   }
   my @script = <P>;
   close P;
   my $newsize = 0;
   my $badedit = 0;
   for (@script) {
      my $oldlen = length();
      if ( $oldlen ) {
          # do your edits here, and:
          my $newlen = length()
          unless ( $newlen ) { # maybe you would check other stuff...
              warn "Oops -- bad edit for $name; check $name.new\n";
              $badedit++;
          }
          $newsize += $newlen;
       }
   }
   unless (open(P,">$name.new")) {
      die "can't seem to open a new version of $name: $!";
   }
   print P for (@script);
   close P;
   if ( -s "$name.new" == $newsize and not $badedit ) {
      rename "$name.new", $name;
   } else {
      die "couldn't write a complete edited version of $name\n";
   }
}