This is an internal function used by formats, though you may call it,
too. It formats (see perlform) a list of values according to the
contents of PICTURE, placing the output into the format output
accumulator, $^A (or $ACCUMULATOR in English).
Eventually, when a write is done, the contents of
$^A are written to some filehandle, but you could also read $^A
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 ~ and ~~ 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 format compiler.
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 perlform for other examples.