in reply to
How to pass form data from a CGI script to its child process?
I surely would have to write code which encodes the form data for the command line (all character sequences which might be treated specially by the shell would have to be transformed), and the form data might be very long, even longer than the maximum length which is allowed for a command line.
You could use CGI
SAVING THE STATE OF THE SCRIPT TO A FILE:
and reading it
my $q = CGI->new(\*IN);
so when you use the list form of system,
system $^X, 'scriptB.pl', 'some/file/something';