In particular I would substitute the --- with the name of hash variable.

No you wouldn't

 
$ perl -MYAML -e " print Dump  { test => { 1 .. 4 } } "
---
test:
  1: 2
  3: 4

$ perl -MYAML -e " print Dump  yaml => { test => { 1 .. 4 } } "
--- yaml
---
test:
  1: 2
  3: 4

$ perl -MDDS -mYAML -e " Dump( YAML::Load( YAML::Dump( { test => { 1 .
+. 4 } } ) ) )"
$HASH1 = { test => {
           1 => 2,
           3 => 4
         } };

$ perl -MDDS -mYAML -e " Dump( YAML::Load( YAML::Dump( yaml => { test 
+=> { 1 .. 4 } } ) ) )"
$VAR1 = 'yaml';
$HASH1 = { test => {
           1 => 2,
           3 => 4
         } };
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