You have the following:

$history{ $+{ ticket } }{ $entry->{ action } } = {
                                     date  => $words[0],
                                    'time' => $words[1],
  ( exists ( $+{ order } ) ? (       order => $+{ order } ) : () ),
  ( exists ( $+{ invoice } ) ? (   invoice => $+{ invoice } ) : () ),
  ( exists ( $+{ shipment } ) ? ( shipment => $+{ shipment } ) : () ),
  ( exists ( $+{ scheduled_date } ) ? (
                            scheduled_date => $+{ scheduled_date } ) : () ),
  ( exists ( $+{ status } ) ? (     status => $+{ status } ) : () ),
};

That's a lot less readable than then following:

$history{ $+{ ticket } }{ $entry->{ action } } = {
                                     date           => $words[0],
                                     time           => $words[1],
  ( exists( $+{ order          } ) ? order          => $+{ order          } : () ),
  ( exists( $+{ invoice        } ) ? invoice        => $+{ invoice        } : () ),
  ( exists( $+{ shipment       } ) ? shipment       => $+{ shipment       } : () ),
  ( exists( $+{ scheduled_date } ) ? scheduled_date => $+{ scheduled_date } : () ),
  ( exists( $+{ status         } ) ? status         => $+{ status         } : () ),
};

It can be further cleaned using a loop.

$history{ $+{ ticket } }{ $entry->{ action } } = {
   date => $words[0],
   time => $words[1],
   (\%+)->%{ grep exists( $+{ $_ } ), qw(
      order
      invoice
      shipment
      scheduled_date
      status
   ) }
};
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The mess can be hidden in a sub.

sub kv { my $h = shift; $h->%{ grep exists( $h->{ $_ } ), @_ } }

kv( \%+, qw( ... ) )
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---

We can simplify further if we don't need 100% equivalence.

If you don't care about undef fields, it simplifies to the following:

$history{ $+{ ticket } }{ $entry->{ action } } = {
   date => $words[0],
   time => $words[1],
   (\%+)->%{qw(
      order
      invoice
      shipment
      scheduled_date
      status
   )}
};
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If there are no extra captures (or you don't care if they end up as extra fields), it simplifies to the following:

$history{ $+{ ticket } }{ $entry->{ action } } = {
   date => $words[0],
   time => $words[1],
   %+,
};
[download]