Its impossible to guess :)

Too many unknown moving parts

Try again please, for example like this

my $input = [ ... ];
my $want = { ... };
my $result = synch_that_time( $before );

require Test::More;
Test::More::is(
  $input,
  $want,
  ' synch_that_time works as designed',
);
[download]

Where you generate $input with liberal sprinkling of Data::Dump in the above script