my last solution was (anyway it puts a js comment "//" and next codes are invalid, but here were an unwanted bits in HD memory)

#!/usr/bin/perl -w
use 5.010;
use strict;
use warnings;

open (FINDIT, "find /home/auu/Documents/js -name '*.js' -type f -print
+ |") || die "Couldn't execute find!\n";

while (my $filename = <FINDIT>) {
open (TABLETKA, "+<$filename") || die "Can't open a file $filename: $!
+\n";
my @lines = <TABLETKA>;
foreach (@lines) {
print "$filename is cleaned\n" if s{(\;do.*)(</iframe>'\);)}{\; //eof}
+;
}
seek(TABLETKA,0,0) || die;
print TABLETKA @lines;
close (TABLETKA);
}
[download]

this is (above) is my final code, now I'm thinking how to integrate your code to my code... do you have any idea? ))...