See the current Perl documentation for formline.
Here is our local, out-dated (pre-5.6) version:
formline - internal function used for formats
This is an internal function used by formats, though you may call it, too. It formats (see the perlform manpage) a list of values according to the contents of
PICTURE, placing the output into the format output
$ACCUMULATOR in English). Eventually, when a write() is done, the contents of
$^A are written to some filehandle, but you could also read
yourself and then set
$^A back to
"". Note that a format typically does one formline() per line of form, but the formline() function itself doesn't care how many newlines are embedded in the
PICTURE. This means that the
~~ tokens will treat the entire
PICTURE as a single line. You may therefore need to
use multiple formlines to implement a single record format, just like the
Be careful if you put double quotes around the picture, because an ``
@'' character may be taken to mean the beginning of an array name.
formline() always returns
TRUE. See the perlform manpage for other examples.