What's a "theme icon"? I suspect I may know what you're actually asking, but given previous events why not take the time to ask a specific question in a way that it is easily understood by others. A link to How do I post a question effectively? is displayed by default every time you post, see also I know what I mean. Why don't you?.

what perl do with

use FreeDesktop::Icons;
my $iconlib = new FreeDesktop::Icons;
$iconlib->theme('WhiteSur-red');
$iconlib->size('16');
my $imagefile = $iconlib->get('xfsm-shutdown');
print $imagefile;
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it's slow and inadequate

That module was first uploaded to CPAN in May. The author probably published it as soon as it met his needs. If you ask nicely, maybe he could help add a feature to do what you need, too.

gi.require_version('Gtk', '3.0')
from gi.repository import Gtk
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I just need to embrace python

Many perl module just fill up CPAN, and help little.

I'm frustrated on perl pdf module once Re^6: use PDF::API2 to add pdf bookmark, perl should not fail me on resolve icon path. Gtk3::Image seems promising, I do some search and check on 'Gtk' and icon theme related and missed Gtk3. I love perl, he has the ability to enpower individual, I'm learning Raku too.

perl should not fail me on resolve icon path

You mean CPAN. Perl can do anything you want, if you write out the full program. You want someone else to solve the problem and post a complete module for you, for all tasks you can think of? There are many many things that Perl does not have a CPAN module for, and yes, Python has more modules to solve the latest problems because Python has more people.

We at perlmonks use perl because we like the language, not because it has the most problems already solved in a module.

On my computer, for example, the Windows system icons are stored mostly in C:\Windows\System32\Shell32.dll and also in C:\Windows\System32\moricons.dll and C:\Windows\Explorer.exe. But by modifying the Windows registry, you can change the system icons to a different theme. Unfortunately, Windows registry is kind of messy, and changing the icon theme on a system is a nightmare if you try to do it one by one. There are hundreds of registry entries that have to be changed. There is a program called Icon Tweaker and another one called Stardock IconPackager. The latter one is paid software. They both let you change the icon theme set of Windows with just one or two clicks.

I'm not sure if this answer is what you're looking for.

You didn't specify what operating system your question is related to. Are you talking about Linux icons or Windows icons or Apple MacBook icons or Android icons? You did not mention if you were referring to icons within a certain program. For example, you can change the icon set within Explorer in Windows. You can change the icon set within your web browser toolbar or the possibilities are endless. Your question is incomplete. It feels like you are expecting people to be able to read your mind and give you a precise answer just like Nebuchadnezzar in the Bible wanted the astrologers and wise men to tell him what his dream was.

see my updated demo