use Encode;

# create a string with one character
my $a = "\x{100}";

# create a string with two characters

my $b = Encode::encode_utf8($a); # Equivalent to $b = "\x80\xc4";

print $b; # outputs the two bytes C4 80

binmode(STDOUT, ":utf8");

print $a; # outputs the two  bytes C4 80
print $b; # outputs the four bytes C3 84 C2 80