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

my @seq1 = qw(ATGC TGCT GCTA CTAA GTCA TAAC );
my @seq2 = qw(GTCA TGCT);
my $i = 0;

foreach my $array1Element (@seq1) {
    foreach my $array2Element (@seq2) {
	if ($array1Element eq $array2Element) {
	    print "Matched: " . $array1Element . " at possition " . $i . " of \@seq1.\n";
	}
    }
    $i++;
}

__END__

Matched: TGCT at possition 1 of @seq1.
Matched: GTCA at possition 4 of @seq1.