#!perl
use strict;
use warnings;

my $seq = "ATCGGCGCCTAT" ;
my (%first,%second,%third);
#perlre
my @trilet = $seq =~ /.../g;
#perlsyn LOOP
foreach my $letter ('A','T','G','C') { #init
	$first{ $letter }=0;
	$second{ $letter }=0;
	$third{ $letter }=0;
}
foreach my $tri (@trilet) {
	#perlfunc : substr
	$first{ substr $tri,0,1 }++;
	$second{ substr $tri,1,1 }++;
	$third{  substr $tri,2,1 }++;
}
foreach my $letter ('A','T','G','C') {
	print "$letter=$first{$letter}; ";
}
print "\n";
foreach my $letter ('A','T','G','C') {
	print "$letter=$second{$letter}; ";
}
print "\n";
foreach my $letter ('A','T','G','C') {
	print "$letter=$third{$letter}; ";
}
print "\n";