knoppix@Microknoppix:~$ perl -E '
> $seq = q{ACTGTGGCGTCAACTG};
> say $seq;
> ( $revSeq = $seq ) =~ tr{ATCG}{TAGC};
> say $revSeq;'
ACTGTGGCGTCAACTG
TGACACCGCAGTTGAC
knoppix@Microknoppix:~$