Have you looked at How do I compute the difference of two arrays? How do I compute the intersection of two arrays??
Also Delete from array has some interesting comments on this sort of thing..

open (FILE1, "<tabtext.txt") or die $!;
open (FILE2, ">ludo.txt") or die $!;
my $re = join "|", map {quotemeta} @params;
while (<FILE1>) {
    print FILE2 if /$re/o;
}
close(FILE1);
close(FILE2);
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--

flounder

open (FILE1, "<tabtext.txt");
open (FILE2, ">ludo.txt");
foreach my $paramKey (@params){
    while(<FILE1>){
        if (/$paramKey.*$/){
            print FILE2, "\n";
    }
}
close(FILE1);
close(FILE2);
[download]

It doesn't print anything in the file! Why?

Because open (FILE2, ">ludo.txt"); overwrites ludo.txt every time through the $paramKey loop.

--

flounder

1. an array with your form values (@params)
2. and a file to select lines from, depending on the values?

If this is it, your approach is not so much wrong. You should consider swapping the loops. You won't need any indexing then.

BTW: Is this homework?

o you mean swapping the "foreach" loop and the "while" one? like this?

open (FILE1, "<tabtext.txt");
open (FILE2, ">ludo.txt");
while(<FILE1>){
    foreach my $paramKey (@params){
        if (/$paramKey/){
            print FILE2;
        }
    }
}
close(FILE1);
close(FILE2);
[download]

and it's not an homework!! LOL

I really recommend the book: Mastering Regular Expressions