my $x1 = $r << 32 | $t;
printf "\nThe value is 0x%x", $x1;   # 0x23400000345

##</code><code>##

use bigint; 

my $r = 0x234;
my $t = 0x345;

my $x1 = $r << 32 | $t;

print $x1->as_hex;