my $s = "A\r\n";
say "@{[map{sprintf '%02X', $_} unpack 'C*', $s]}"; # 41 0D 0A
say chomp $s;                                       # 1
say "@{[map{sprintf '%02X', $_} unpack 'C*', $s]}"; # 41 0D

# ändere die Voreinstellung für $/
$/ = "\r\n";
$s = "B\r\n";
say chomp $s;                                       # 2
say "@{[map{sprintf '%02X', $_} unpack 'C*', $s]}"; # 42