diff --git a/lib/Subtitle/SSA/Event.pm b/lib/Subtitle/SSA/Event.pm
index ec23e31..9999ff5 100644
--- a/lib/Subtitle/SSA/Event.pm
+++ b/lib/Subtitle/SSA/Event.pm
@@ -23,6 +23,34 @@ my %FIELDS = (
   effect  => { type => 's', value => '',         name => 'Effect'  },
   text    => { type => 's', value => '',         name => 'Text'    },
 );
-my $PREFIX = 'Dialogue';
+
+# options:
+#  * version - 'ssa' for v4 or 'ass' for v4+
+sub new {
+  my ($class, %opts) = @_;
+  my $self = {
+    _vers   => 'ass',
+    _fields => \%FIELDS,
+    _format => \@FIELDS_ASS,
+    _prefix => 'Dialogue',
+  };
+
+  if (my $v = $opts{version}) {
+    if ($v =~ m{^(ass|ssa)$}oi) {
+      $self->{_vers} = lc($v);
+    } else {
+      die("unsupported event version $v");
+    }
+  }
+
+  $self->{_format} = \@FIELDS_SSA
+    if $self->{_vers} eq 'ssa';
+
+  my @fields = $self->{_fields};
+  $self->{$_} = $FIELDS{$_}->{value}
+    foreach @fields;
+
+  return bless($self, $class);
+}
 
 1;
diff --git a/lib/Subtitle/SSA/Record.pm b/lib/Subtitle/SSA/Record.pm
index cbdb051..c3543a7 100644
--- a/lib/Subtitle/SSA/Record.pm
+++ b/lib/Subtitle/SSA/Record.pm
@@ -6,50 +6,16 @@ use utf8;
 
 use Subtitle::Utils qw(:timing);
 
-use overload => (
+use overload
   '""' => \&to_string,
-);
-
-my %FIELDS = (); # must be redefined in subclass
-my $PREFIX = ''; # must be redefined in subclass
-
-# options:
-#  * version - 'ssa' for v4 or 'ass' for v4+
-sub new {
-  my ($class, %opts) = @_;
-  my $self = {
-    _vers => 'ass',
-  };
-  bless($self, $class);
-
-  if ($opts{version} and $opts{version} =~ m{^(ass|ssa)$}oi) {
-    $self->{_vers} = lc($opts{version});
-  }
-
-  my @fields = $self->fields();
-  $self->{_fieldcnt} = scalar @fields;
-  foreach my $field (@fields) {
-    $self->{$field} = ($opts{defaults})
-      ? $FIELDS{$field}->{value}
-      : undef;
-  }
-
-  return $self;
-}
-
-sub fields {
-  my ($self) = @_;
-  return ($self->{_vers} eq 'ssa')
-    ? @FIELDS_SSA
-    : @FIELDS_ASS;
-}
+;
 
 sub set {
-  my ($self, $opt, $value) = @_;
-  return unless $opt;
-  $opt = lc($opt);
-  return unless exists $self->{$opt};
-  $self->{$opt} = $value;
+  my ($self, $field, $value) = @_;
+  return unless $field;
+  $field = lc($field);
+  return unless exists $self->{$field};
+  $self->{$field} = $value;
   return 1;
 }
 
@@ -59,12 +25,12 @@ sub parse_format_line {
   return unless $line and $line =~ m{^Format:}oi;
 
   chomp $line;
-  $line =~ s{^Format:\s+}{}oi;
+  $line =~ s{^Format:\s*}{}oi;
 
   my @fields;
   foreach my $field (split(/,\s*/o, $line)) {
     $field = lc($field);
-    return unless exists $FIELDS{$field};
+    return unless exists $self->{_fields}->{$field};
     push @fields, $field;
   }
 
@@ -79,22 +45,25 @@ sub parse_format_line {
 #  f - float, 6.01 or 6 if no fractional part
 #  x - hex-number, &H00AABBCC for ASS or decimal number for SSA
 sub parse {
-  my ($self, $fields, $line) = @_;
+  my ($self, $line, $format) = @_;
+  $format //= $self->{_format};
 
-  return unless $fields and ref($fields) eq 'ARRAY';
+  my $PREFIX = $self->{_prefix};
   return unless $line and $line =~ m{^$PREFIX:}oi;
+  return unless $format and ref($format) eq 'ARRAY';
 
   chomp $line;
   $line =~ s{^$PREFIX:\s*}{}oi;
-  my @values = split /,\s*/o, $line, $self->{_fieldcnt};
+  my $fieldcnt = scalar @{ $format };
+  my @values = split /,\s*/o, $line, $fieldcnt;
   # check that values count match fields count
-  return unless scalar @{ $fields } != scalar @values;
+  return if scalar @values != $fieldcnt;
 
-  foreach my $field (@{ $fields }) {
-    my $d = $FIELDS{$field};
+  foreach my $field (@{ $format }) {
+    my $d = $self->{_fields}->{$field};
     my $value = shift @values;
-    if ($t->{type} eq 'x' and $value =~ m<&H([0-9a-f]{8})>oi) {
-      $value = unpack("H8", $1);
+    if ($d->{type} eq 'x' and $value =~ m<&H([0-9a-f]{8})>oi) {
+      $value = hex($1);
     } elsif ($d->{type} eq 't') {
       $value = parse_timing($value);
       return if $value < 0; # parsing failure
@@ -107,15 +76,13 @@ sub parse {
 
 sub to_string {
   my ($self) = @_;
-  my @fields = $self->fields();
-  my $string = $PREFIX . ' ';
+  my $string = $self->{_prefix} . ' ';
   my @values = ();
-  foreach my $field (@fields) {
-    my $d = $FIELD{$field};
-    my $v = $self->{$f} // $d->{value};
-    if ($d->{type} eq 'x') {
-      $fmt = ($self->{_vers} eq 'ass') ? '&H%08X' : '%d';
-      $v = sprintf $fmt, $v;
+  foreach my $field (@{ $self->{_fields} }) {
+    my $d = $self->{_fields}->{$field};
+    my $v = $self->{$field} // $d->{value};
+    if ($d->{type} eq 'x' and $self->{_vers} eq 'ass') {
+      $v = sprintf '&H%08X', $v;
     } elsif ($d->{type} eq 'f') {
       $v = sprintf "%.2f", $v;
       # hack: make decimal from float if fractional part is zero after round up
diff --git a/lib/Subtitle/SSA/Style.pm b/lib/Subtitle/SSA/Style.pm
index 79ba97d..9137074 100644
--- a/lib/Subtitle/SSA/Style.pm
+++ b/lib/Subtitle/SSA/Style.pm
@@ -37,6 +37,34 @@ my %FIELDS = (
   alphalevel        => { type => 'd', value =>   0, name => 'AlphaLevel' },
   encoding          => { type => 'd', value => 204, name => 'Encoding' },
 );
-my $PREFIX = 'Style';
+
+# options:
+#  * version - 'ssa' for v4 or 'ass' for v4+
+sub new {
+  my ($class, %opts) = @_;
+  my $self = {
+    _vers   => 'ass',
+    _fields => \%FIELDS,
+    _format => \@FIELDS_ASS,
+    _prefix => 'Style',
+  };
+
+  if (my $v = $opts{version}) {
+    if ($v =~ m{^(ass|ssa)$}oi) {
+      $self->{_vers} = lc($v);
+    } else {
+      die("unsupported event version $v");
+    }
+  }
+
+  $self->{_format} = \@FIELDS_SSA
+    if $self->{_vers} eq 'ssa';
+
+  my @fields = @{ $self->{_format} };
+  $self->{$_} = $FIELDS{$_}->{value}
+    foreach @fields;
+
+  return bless($self, $class);
+}
 
 1;