[puppet] How to print something when running Puppet client?

You could go a step further and break into the puppet code using a breakpoint.

http://logicminds.github.io/blog/2017/04/25/break-into-your-puppet-code/

This would only work with puppet apply or using a rspec test. Or you can manually type your code into the debugger console. Note: puppet still needs to know where your module code is at if you haven't set already.

gem install puppet puppet-debugger 
puppet module install nwops/debug
cat > test.pp <<'EOF'
$var1 = 'test'
debug::break()
EOF

Should show something like.

puppet apply test.pp
From file: test.pp
     1: $var1 = 'test'
     2: # add 'debug::break()' where you want to stop in your code
  => 3: debug::break()
1:>> $var1
=> "test"
2:>>

https://www.puppet-debugger.com