LibXML.c: loadable library and perl binaries are mismatched

[RS]

I have been running get_iplayer under Kubuntu 18,04 for a long time.  I 
used to use the Jon Hedgerows PPA.  When that was withdrawn I followed 
the suggestions in the installation instructions to remove the PPA and 
to create a manual installation.  This has run without problems for a 
long time, although I was still running v3.28.

I have just upgraded from Kubuntu 18.04.6 LTS to Kubuntu 20.04.4 LTS. 
Now whenever I try to run get_iplayer, with or without arguments, it 
immediately displays a message

LibXML.c: loadable library and perl binaries are mismatched (got 
handshake key 0xde00080, needed 0xcd00080)

It does not even display the version number.

I have looked at a number of discussions on stackoverflow and github. 
As far as I can make out the error message means that modules have been 
compiled with different versions of Perl.  I have tried re-installing 
all the modules.  I just tells me

libcgi-pm-perl is already the newest version (4.46-1).
liblwp-protocol-https-perl is already the newest version (6.07-2ubuntu2).
libwww-perl is already the newest version (6.43-1).
libxml-libxml-perl is already the newest version (2.0134+dfsg-1build1).
libmojolicious-perl is already the newest version (8.33+dfsg-1).

The Perl version appears to be 5.30.0  I have also installed v3.30 of 
get_iplayer.  None of this makes any difference.

Does anyone have any ideas as to what else I should look at, and how to 
fix it?

Best wishes
Richard