How to solve "Can't locate TXK/ARGS.pm in @INC (you may need to install the TXK::ARGS module)" when running txkChkPDBCompatability.pl

Background:

As a part of converting your non-CDB Oracle database to a pluggable database, you are supposed to run the perl script txkChkPDBCompatability.pl

Problem:

The script fails with:

Can't locate TXK/ARGS.pm in @INC (you may need to install the TXK::ARGS module) (@INC contains: $ORACLE_HOME/perl/lib/5.28.1/x86_64-linux-thread-multi $ORACLE_HOME/perl/lib/5.28.1 $ORACLE_HOME/perl/lib/site_perl/5.28.1/x86_64-linux-thread-multi $ORACLE_HOME/perl/lib/site_perl/5.28.1 $ORACLE_HOME/perl/lib/site_perl/5.28.1/x86_64-linux-thread-multi /$ORACLE_HOME/perl/lib/site_perl/5.28.1 $ORACLE_HOME/perl/lib/5.28.1/x86_64-linux-thread-multi $ORACLE_HOME/perl/lib/5.28.1) at ./txkChkPDBCompatability.pl line 61.
BEGIN failed--compilation aborted at ./txkChkPDBCompatability.pl line 61.

Cause:

The PERL5LIB environment variable is not complete. You need to add the location of the ADK and TXK directories, which in turn contains several .pm files.
These folders can be found in $ORACLE_HOME/appsutil/perl

Solution:

Add the $ORACLE_HOME/appsutil/perl to your existing PERL5LIB variable:

export PERL5LIB=$PERL5LIB:$ORACLE_HOME/appsutil/perl

Thanks to the author of Punitoracledba for providing the solution after lots of troubleshooting.

To see the note used to convert a non-cdb EBS database to a pluggable database, go to Doc ID 2552181.1 at Oracle Support