@sequences = (ATATGACTTG,
GGGGATCCAC,
ATACATATAC,
AGGCTACGCT,
GAGGCCGCGC);

@list = sort GC @sequences;


sub GC{
$count = 0; #keep count of g and c per sequence
$index = 0; #cycle through each item in list
for ($count = 0; { #Not sure, I've tried many things.
if(g == $sequences{$index}) {$total = $count + 1}
if(c == $sequences{$index}) {$total = $count + 1}
$index++;
return($a cmp $b);
}
}

print join("\n", @list), "\n";