# in the code
my $arg = hex(shift @ARGV);

##</code><code>##

my $arg = chr hex(shift @ARGV);

##</code><code>##

my $sep = pack "H2", (shift @ARGV);  # with input being 'd1', for example

##</code><code>##

my $sepArg = shift @ARGV;
my ($hex) = $sepArg =~ /\\x([\da-fA-F]+)/;
my $sep = chr hex $hex;
my $str = "field1 $sep field2";

##</code><code>##

my $sepArg = shift @ARGV;            # input being '\xd1', for example
my $str = eval qq("field1 $sepArg field2");