me@BothMachines: perl -e'use warnings; print undef; print "done\n";'
Use of uninitialized value in print at -e line 1.
done

me@BothMachines: cat test.pl
#!/usr/bin/perl
use strict;
use warnings;
print undef;
print "done\n";

me@BothMachines: ./test.pl 
Use of uninitialized value in print at ./test.pl line 4.
done