Based on the limited information you've provided I assume you wish to execute two grep statements per filename.

But first, even though this might be a simple script, simple scripts have a habit of growing and evolving over time, so start it out properly at the beginning.
use strict *ALWAYS*
use warnings
use a standard formatting and indentation style (i like K&R)

Give this a try:

#!/usr/bin/perl
use strict;
use warnings;

my @filename = qw{filename1 filename2 filename3};
my @data =qw{DATA1 DATA2};

foreach my $file (@filename) {
    foreach my $searchdata (@data) {
        my $cmd_results = `grep -c $searchdata $file`;
        print "$file | $searchdata | $cmd_results \n"; # or whatever t
+ags refers to...
    }
}
[download]

It may be worth noting that your original method would have run into problems once $i reaches 2 (and tries to process DATA3 which doesn't exist...)
Using a foreach is nice since you don't need to care about an iterator, and you can make the code more self documenting... IMHO