Thanks so much to all of you! I've learned a lot, even where there was disagreement about package and module naming rules.

I'm definitely going to install portable Strawberry, but before I do I want to understand why Perl is barfing. All package and module name references are now in CamelCase (Plx, PlxHml and PlxLang), and all modules export their unique variable and subroutine names into main. None of the modules issue "use" statements, leaving that responsibility to the calling scripts that need the exported resources. I no longer get any "duplicate definition" warnings.

BUT: Even though (thanks to "$Exporter::Verbose=1;"), I know that the x_log subroutine is being exported into main, I still get the following fatal error when I run a script that uses Plx, PlxHml and PlxLang:

c:\()hml.pl
Carp::EXPORT_FAIL cached: verbose &verbose at C:/Perl64/lib/Exporter/H
+eavy.pm line 173.
Importing into Carp from Carp: carp, confess, croak at C:/Perl64/lib/E
+xporter/Heavy.pm line 192.
Importing into main from Plx: $PLX_DIAGS, $PM_PLX, &FALSE, &LINE_LEN, 
+&MAX_SIGNED, &MAX_UNSIGNED, &MIN_SIGNED, &MIN_UNSIGNED, &NO, &NUMBER,
+ &STRING, &TRUE, &UND
EFINED, &YES, &x_abort_retry_ignore, &x_as_dos_operand, &x_as_integer,
+ &x_as_power_of_1024, &x_as_string, &x_beep, &x_bytes, &x_bytes_free,
+ &x_caption_2_html, &
x_caption_2_text, &x_cardinal, &x_cgi, &x_change_all, &x_con_exp, &x_c
+onsole, &x_cookies, &x_current_dir, &x_current_drive, &x_decompile, &
+x_dump, &x_dump_calle
rs, &x_dump_diags, &x_dump_env, &x_dump_params, &x_elapsed_time, &x_em
+ail_address_in_words, &x_env, &x_eta, &x_exp, &x_expand_filespec, &x_
+explore, &x_file, &x_
file_yyyymmdd, &x_file_yyyymmdd_hhmmss, &x_filetest, &x_flowerbox, &x_
+folder_is_an_archive, &x_format_date_and_time, &x_format_filetest_tim
+e, &x_format_filetime
, &x_format_rfc_822_date_and_time, &x_gallery, &x_get_parm, &x_get_str
+ing, &x_goto, &x_hh_mm, &x_hh_mm_ss, &x_hhmm, &x_hhmmss, &x_in_bytes,
+ &x_in_gigabytes, &x_
in_kilobytes, &x_in_megabytes, &x_in_petabytes, &x_in_terabytes, &x_in
+terpolate, &x_is_a_dir, &x_is_a_file, &x_is_drive_offline, &x_is_driv
+e_online, &x_log, &x_
log_cgi, &x_log_cookies, &x_log_dir, &x_log_env, &x_log_error, &x_log_
+exp, &x_log_file, &x_log_prefix, &x_log_running, &x_logging_to_browse
+r, &x_logging_to_cons
ole, &x_logging_to_disk, &x_matches, &x_mm_dd_yyyy, &x_monitor, &x_not
+ify, &x_option_list, &x_ordinal, &x_package_variables_in_javascript, 
+&x_parse_filespec, &x
_parse_imgsrc, &x_pause, &x_percent, &x_prog_spec, &x_running, &x_sani
+ty, &x_save, &x_seconds_have_elapsed, &x_signal, &x_sing_plur, &x_sof
+t_breaks, &x_squeeze,
 &x_started_ended_taking, &x_status, &x_string_2_symbol, &x_system, &x
+_time, &x_type, &x_user, &x_val, &x_val_style, &x_val_tab, &x_val_tru
+nc, &x_with_commas, &
x_words, &x_work_dir, &x_yes_or_no, &x_yyyy, &x_yyyy_mm_dd_hh_mm_ss, &
+x_yyyymm, &x_yyyymmdd at C:\!dh\DH\COM\SRC\hml.pl line 206
        main::BEGIN() called at (#2) line 206
        eval {...} called at (#2) line 206
Undefined subroutine &PlxHml::x_log called at C:/Perl64/site/lib/PlxHm
+l.pm line 47.
Compilation failed in require at C:\!dh\DH\COM\SRC\hml.pl line 207.
BEGIN failed--compilation aborted at C:\!dh\DH\COM\SRC\hml.pl line 207
+.
[download]

What should I try now?

Your code tries to call &PlxHml::x_log, but your posted source code has:

package PLXHML;
[download]

So, x_log at best lives in PLXHML::x_log.

This somewhat runs counter to your assertion that now all references and filenames are in CamelCase, so maybe you can reduce your code to a short, self-contained example that still exhibits the problem you have.

The next best thing likely is to look at line 47 of PlxHml.pm and see what routine is called there.

Start removing code from PlxHml.pm until you have around 20 lines that reproduce the problem.

Update: I think I have it somewhat wrong - from the log posted above, Plx exports x_log into main::, but nothing exports into PlxHml. But somewhere in PlxHml.pm your code looks like the following:

package PlxHml;
use strict;

sub foo {
    x_log(...);
};
[download]

Most likely, then you will need to import Plx into PlxHml as well:

package PlxHml;
use strict;
use Plx;

sub foo {
    x_log(...);
};
[download]

None of the modules issue "use" statements


Do you now have this

package PlxHml; # was PLXHML
#  use PLX; <- removed
use Carp;
$SIG{__WARN__} = \&carp;
$SIG{__DIE__} = \&confess;
[download]

and x_log is defined in Plx ?

poj

Yes, I gave PlxHml.pm the package name PlxHml, and removed the "use Plx;" statement. x_log is indeed defined in Plx.
I thought I had been told that exporting into main made the resource available to all modules, but I guess I misinterpreted what I heard. So I just added the use statements back into each module. Plx now uses PlxHml and PlxLang, PlxHml now uses Plx and PlxLang, and PlxLang now uses Plx and PlxHml. All scripts include all 3 "use" statements.
Now I'm getting

c:\()hml.pl
Undefined subroutine &PlxHml::x_log called at C:/Perl64/site/lib/PlxHm
+l.pm line 50.
Compilation failed in require at C:/Perl64/site/lib/Plx.pm line 128.
BEGIN failed--compilation aborted at C:/Perl64/site/lib/Plx.pm line 12
+8.
Compilation failed in require at C:\!dh\DH\COM\SRC\hml.pl line 206.
BEGIN failed--compilation aborted at C:\!dh\DH\COM\SRC\hml.pl line 206
+.
[download]

Line 50 of PlxHml.pm is

x_log("\n($PM_PLXHML)");

Line 128 of Plx.pm is

use PlxHml;

And line 206 of hml.pl is

use Plx;