c:\@Work\Perl>perl -wMstrict -le
"my $sequence = 'xxxGCxxCxxxxCGxGxxxGxxxxxCxx';
 ;;
 my $sequencelength = length $sequence;
 print qq{sequence length: $sequencelength};
 ;;
 my $GCcount = $sequence =~ tr/GC//;
 print qq{total Gs and Cs: $GCcount};
 ;;
 my $GCcontent = ($GCcount / $sequencelength) * 100;
 print qq{GCcontent: $GCcontent percent}
"
sequence length: 28
total Gs and Cs: 8
GCcontent: 28.5714285714286 percent