Apparently, a recent Red Hat Enterprise Linux update for ES3, 4 and 5 caused some Perl applications to throw errors like these:

unable to call function somefunction on undefined value

Of course, replace somefunction with your function of choice. To correct the issue, you can force CPAN to bring back a more sane version of Scalar::Util:

# perl -MCPAN -e shell
cpan> force install Scalar::Util