#!/usr/bin/perl -w

sub concatenate {
	my($string1,$string2) = @_;
	my $concatenation = $string1.$string2;
	return $concatenation;
}

sub revcom {
	my ($dna) = @_;
	my $revcom = reverse $dna;
	$revcom =~ tr/ACGTacgt/TGCAtgca/;
	return $revcom;
}

sub countNs {
	my ($dna) = @_;
	my $As = ($dna =~ tr/Aa//); 
	my $Gs = ($dna =~ tr/Gg//); 
	my $Cs = ($dna =~ tr/Cc//); 
	my $Ts = ($dna =~ tr/Tt//); 
	return ($As,$Gs,$Cs,$Ts);
}