rail, 65 bytes

Result

WA

Code [DL]

$ 'x'
 \
  \-(!a!)(!b!)(a)(b)#

$ 'main'
 \
  \-[hoge][piyo]{x}o#

stdin

4305783289395320626390270382739107366586646424247458708936031273801917752156961346528063342606997978

stdout

hoge

stderr

strace