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lib/Astro/FITS/Header.pm  view on Meta::CPAN

Comment cards are a special case because they have no normal value and
their comment field is treated as the hash value.  The keywords
"COMMENT" and "HISTORY" are magic and refer to comment cards; nearly all other
keywords create normal valued cards.  (see "SIMPLE and END cards", below).

=head2 Multi-card values

Multiline string values are broken up, one card per line in the
string.  Extra-long string values are handled gracefully: they get
split among multiple cards, with a backslash at the end of each card
image.  They're transparently reassembled when you access the data, so
that there is a strong analogy between multiline string values and multiple
cards.

In general, appending to hash entries that look like strings does what
you think it should.  In particular, comment cards have a newline
appended automatically on FETCH, so that

  $hash{HISTORY} .= "Added multi-line string support";

adds a new HISTORY comment card, while

lib/Astro/FITS/Header.pm  view on Meta::CPAN

# store key and value pair
#
# Multiple-line kludges (CED):
#
#    * Array refs get handled gracefully by being put in as multiple cards.
#
#    * Multiline strings get broken up and put in as multiple cards.
#
#    * Extra-long strings get broken up and put in as multiple cards, with
#      an extra backslash at the end so that they transparently get put back
#      together upon retrieval.
#

sub STORE {
  my ($self, $keyword, $value) = @_;
  my @values;

  # Recognize slash-delimited comments in value keywords.  This is done
  # cheesily via recursion -- would be more efficient, but less readable,
  # to propagate the comment through the code...