G'day miguelnixon.

Welcome to the Monastery.

"... forgive me if this is the wrong forum ..."

No need to seek forgiveness. Feel free to ask any Perl-related questions here. And please don't be dissuaded by thinking you should already know something: I, with apparently more than five years of Perl under my belt than you, asked a perldoc-related question just last week.

I suspect the differences you're seeing are OS-related, not Perl-related. There may be some configuration (or similar) setting you need to change such that "heading." becomes an equivalent with formatting code like ".[1m.[1mheading.[0m.[0m.".

$ env | grep PAGE
PAGER=/usr/bin/less
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I don't have your OS/Perl combination available. This makes testing your specification installations impossible for me; however, general test scenarios are valid for us both. I do have Perl 5.30 on Cygwin (but nothing as early as 5.22). The following reflects my tests with 5.30 (I repeated these with 5.34 — my usual and latest, currently stable version — but saw no differences).

I wrote pm_11136178_pod_formatting.pod:

=encoding utf8

=head1 Emphases

=over 4

=item * Plain

perldoc Bold, Italic etc

=item * Bold

B<perldoc Bold, Italic etc>

=item * Italic

I<perldoc Bold, Italic etc>

=item * Bold Italic

B<< I<perldoc Bold, Italic etc> >>

=item * Italic Bold

I<< B<perldoc Bold, Italic etc> >>

=item * Bold Italic Code

B<<< I<< C<perldoc Bold, Italic etc> >> >>>

=item * Italic Bold Code

I<<< B<<  C<perldoc Bold, Italic etc> >> >>>

=back

=cut
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Running that through perldoc I get:

Emphases
    *   Plain

        perldoc Bold, Italic etc

    *   Bold

        perldoc Bold, Italic etc

    *   Italic

        *perldoc Bold, Italic etc*

    *   Bold Italic

        *perldoc Bold, Italic etc*

    *   Italic Bold

        *perldoc Bold, Italic etc*

    *   Bold Italic Code

        *"perldoc Bold, Italic etc"*

    *   Italic Bold Code

        *"perldoc Bold, Italic etc"*
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I do note various asterisks and double-quotes to represent emphasis and monospace text; however, there's nothing to differentiate italicised and emboldened text. Did you see something different between 5.22 and 5.30.

Piping the perldoc output through hexdump:

$ perldoc pm_11136178_pod_formatting.pod | hexdump -C
00000000  45 6d 70 68 61 73 65 73  0a 20 20 20 20 2a 20 20  |Emphases.
+    *  |
00000010  20 50 6c 61 69 6e 0a 0a  20 20 20 20 20 20 20 20  | Plain.. 
+       |
00000020  70 65 72 6c 64 6f 63 20  42 6f 6c 64 2c 20 49 74  |perldoc B
+old, It|
00000030  61 6c 69 63 20 65 74 63  0a 0a 20 20 20 20 2a 20  |alic etc.
+.    * |
00000040  20 20 42 6f 6c 64 0a 0a  20 20 20 20 20 20 20 20  |  Bold.. 
+       |
00000050  70 65 72 6c 64 6f 63 20  42 6f 6c 64 2c 20 49 74  |perldoc B
+old, It|
00000060  61 6c 69 63 20 65 74 63  0a 0a 20 20 20 20 2a 20  |alic etc.
+.    * |
00000070  20 20 49 74 61 6c 69 63  0a 0a 20 20 20 20 20 20  |  Italic.
+.      |
00000080  20 20 2a 70 65 72 6c 64  6f 63 20 42 6f 6c 64 2c  |  *perldo
+c Bold,|
00000090  20 49 74 61 6c 69 63 20  65 74 63 2a 0a 0a 20 20  | Italic e
+tc*..  |
000000a0  20 20 2a 20 20 20 42 6f  6c 64 20 49 74 61 6c 69  |  *   Bol
+d Itali|
000000b0  63 0a 0a 20 20 20 20 20  20 20 20 2a 70 65 72 6c  |c..      
+  *perl|
000000c0  64 6f 63 20 42 6f 6c 64  2c 20 49 74 61 6c 69 63  |doc Bold,
+ Italic|
000000d0  20 65 74 63 2a 0a 0a 20  20 20 20 2a 20 20 20 49  | etc*..  
+  *   I|
000000e0  74 61 6c 69 63 20 42 6f  6c 64 0a 0a 20 20 20 20  |talic Bol
+d..    |
000000f0  20 20 20 20 2a 70 65 72  6c 64 6f 63 20 42 6f 6c  |    *perl
+doc Bol|
00000100  64 2c 20 49 74 61 6c 69  63 20 65 74 63 2a 0a 0a  |d, Italic
+ etc*..|
00000110  20 20 20 20 2a 20 20 20  42 6f 6c 64 20 49 74 61  |    *   B
+old Ita|
00000120  6c 69 63 20 43 6f 64 65  0a 0a 20 20 20 20 20 20  |lic Code.
+.      |
00000130  20 20 2a 22 70 65 72 6c  64 6f 63 20 42 6f 6c 64  |  *"perld
+oc Bold|
00000140  2c 20 49 74 61 6c 69 63  20 65 74 63 22 2a 0a 0a  |, Italic 
+etc"*..|
00000150  20 20 20 20 2a 20 20 20  49 74 61 6c 69 63 20 42  |    *   I
+talic B|
00000160  6f 6c 64 20 43 6f 64 65  0a 0a 20 20 20 20 20 20  |old Code.
+.      |
00000170  20 20 2a 22 70 65 72 6c  64 6f 63 20 42 6f 6c 64  |  *"perld
+oc Bold|
00000180  2c 20 49 74 61 6c 69 63  20 65 74 63 22 2a 0a 0a  |, Italic 
+etc"*..|
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That looks a lot like your 5.22 ouput.

In case you were wondering, Cygwin does support highlighting codes. I can't tell how they might differ. Here's an example:

$ echo $PS1
\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n\$
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I would investigate the OS versions differences first. Some monks may even have exactly the same combinations of OS and Perl as you; that may help more than I've been able. If you do find that it's an OS issue; please post here for the benefit of others.

P. S. (forgot to mention): I generated HTML output via:

pod2html --infile=pm_11136178_pod_formatting.pod --outfile=pm_11136178
+_pod_formatting.html
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When viewed in Firefox the output was exactly as expected. All formatting codes had been correctly translated to the equivalent HTML tags.