p4raw-id: //depot/cfgperl@2843
# configure test should be beefed up to try using the field when
# it can't find any of the standardly-named fields.
d_dirnamlen='define'
+
+# Ultrix can mmap only character devices, not regular files,
+# which is rather useless state of things for Perl.
+d_mmap='undef'