package MyModule;
use strict;
use warnings;

my $Dump;
if (eval { require Data::Dump; 1}) {
    $Dump = sub { goto &Data::Dump::dd };
} else {
    require Data::Dumper;
    $Dump = sub { goto &Data::Dumper::Dumper };
}

print "this is %INC:\n";
print $Dump->(\%INC);

__END__