php - How to stop regex match if word is found? -

i have text this:

text 786 opq rts  appendix   title   text 123  abc efg   appendix b  text 456 hij klm 

and

text 786 opq rts  appendix   title   text 123  abc efg   text 456 hij klm 

i'm trying use regex extract text starting appendix a appendix b if appendix b present otherwise appendix a until end (i.e., hij klm). also, appendix a must appear within 15 words before title. i'm come far:

(\b(?:appendix)(?:.){0,15}(?:title)(?:.*)(?:appendix){0,1})/is 

problem is, capture not stop @ appendix b if appendix b there, captures until end.

one way use alternation optional part

perl -0777 -wlne'     @m = /(appendix .{0,15} title (?: .*?appendix\s\w+ | .*) )/xsig;      @m ' input.txt 

with /g match sections within appendix markers.

or capture multiple groups, 1 optional item, test , use accordingly

perl -0777 -wne'     @m = /(appendix .{0,15} title) (.*? appendix\s\w+)? (.*)/xsi;     print join "", ($m[1] ? @m[0,1] : @m[0,2]) ' input.txt 

this works because $2 is created second ( if there no match.

with yet more capture groups can filter in second case, ? grep { defined } @m. if there may multiple appendix-sections better use while $n variables in approach

while (/(appendix.{0,15}title)(.*?appendix\s\w+)?(.*)/sig) {     $appx_section = ($2) ? $1.$2 : $1.$3;     ... } 

since 1 big @m captures need little analysis.

all these print desired output in both cases, including multiple appendix-sections.

i've wrapped in one-liners ready testing. code works in perl script stands.