Edit: /usr/lib64/perl5/CORE/form.h (1463B)
/* form.h
*
* Copyright (C) 1991, 1992, 1993, 2000, 2004, 2011 by Larry Wall and others
*
* You may distribute under the terms of either the GNU General Public
* License or the Artistic License, as specified in the README file.
*
*/
#define FF_END 0 /* tidy up, then return */
#define FF_LINEMARK 1 /* start (or end) of a line */
#define FF_LITERAL 2 /* append
literal chars */
#define FF_SKIP 3 /* skip chars in format */
#define FF_FETCH 4 /* get next item and set field size to */
#define FF_CHECKNL 5 /* find max len of item (up to \n) that fits field */
#define FF_CHECKCHOP 6 /* like CHECKNL, but up to highest split point */
#define FF_SPACE 7 /* append padding space (diff of field, item size) */
#define FF_HALFSPACE 8 /* like FF_SPACE, but only append half as many */
#define FF_ITEM 9 /* append a text item, while blanking ctrl chars */
#define FF_CHOP 10 /* (for ^*) chop the current item */
#define FF_LINEGLOB 11 /* process @* */
#define FF_DECIMAL 12 /* do @##, ^##, where =(precision|flags) */
#define FF_NEWLINE 13 /* delete trailing spaces, then append \n */
#define FF_BLANK 14 /* for arg==0: do '~'; for arg>0 : do '~~' */
#define FF_MORE 15 /* replace long end of string with '...' */
#define FF_0DECIMAL 16 /* like FF_DECIMAL but for 0### */
#define FF_LINESNGL 17 /* process ^* */