If I understand correctly, the reverse complement of a DNA sequence (or string, as it is in Perl) is literally the reverse of the complement of the sequence/string (update: or maybe it's the complement of the reverse :). See reverse.

Win8 Strawberry 5.30.3.1 (64)  Sun 04/25/2021 15:11:49
C:\@Work\Perl\monks
>perl

use 5.014;  # /r modifier for tr///anslation & s///ubstitution

use strict;
use warnings;

my $s = 'ACTGTTCCAAGG';
print "'$s' \n";

$s = reverse $s =~ tr/ATCG/TAGC/r;
print "'$s' \n";

^Z
'ACTGTTCCAAGG'
'CCTTGGAACAGT'
[download]

If your version of Perl does not support the /r translation/substitution modifier (version 5.14+), let us know and alternate code can easily be given.

Update: The result above is also returned for the given input by the http://www.bioinformatics.org/sms/rev_comp.html website | webpage. I'm not a bio-guy, so I hope this means I understand the problem somewhat and the code above is at least minimally useful.