As you may see above in my reply to Cavac's post, there are random "devices" and I can get apparently random numbers. But I'm not actually trying to do anything with random numbers, which is why I find the response to perl -v idiosyncratic. The difference between the working card and the problem cards is that Perl was compiled on the working card and copied from there to the problem cards. Both cards had the same image copied to them using the same computer. Apart from Perl, everything works perfectly on both cards. I cannot see how the problem can be anything other than my failure to copy something from the working card to the problem cards, as the Perl creation process is the only difference. Sorry if my frustration is showing again.