Hiii..guyz..thanks for replying..It's not homework..please be assured..I am just a Biologist interested in Bioinformatics...so not studying in any school right now.. I am really new in Perl..but I am trying..I have wrote a code for it..bt unfortunately it just extracts the matched part..The code I wrote..

while( $dna=<DNA> ) {
#chomp ($dna);


if ($dna =~ /[ACGT]+/) {
 #chomp ($dna);
print  "$&\n";
  }
}
[download]

I do not know how to get the unmatched part..thanks for any help!!