The following is my bare-bones Perl code: #!/fs/COTS/gnu/bin/AIX/perl use bignum ; print Math::BigInt->new("0xbe91cfb586466d02"),"\n"; When I execute this (name:hx2int.pl) on a command line, I get the following which is exactly what I want: 13731985117378145538 After almost sixty years I fear I've probably lost a few bits myself - you're right, I should know about trying to cram ten pounds of manure into a five-pound bag...