Thanks,
My Lexmark X364dn stopped working after the Big Sur upgrade and the driver only reported the Filter-failure error some others mentioned in this thread.
I found that the Perl script /Library/Printers/Lexmark/filter/rerouteprintoptionG2 has already the mentioned change.
It seem s that it was updated on December 1 2020.
By looking to the /var /log/cups/error_log I found that in my case the following Perl script is used:
/Library/Printers/Lexmark/filter/psoptionreroute
And I found the same POSIX reference:
use POSIX qw(tmpnam);
which I replaced with:
se File::Temp qw(tmpnam);
Now the printing is working for me on Big Sur