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{
  meas_1 => {
...
    suffix_5 => { C1 => { value => 0.7 },  C2 => { value => 500.7 } },
  },
}

#!/usr/bin/env perl

...

use Data::Dump;
dd \%ordered_hash;

{
  meas_1 => {
...
    C2 => ["suffix_5", "suffix_4", "suffix_3", "suffix_2", "suffix_1"]
+,
  },
}