python3, 56 bytes

Result

AC

Duration

599ms

Code [DL]

while 1:s=input()+"a";print(s[:s.find("__")].count("|"))

stdin

||_|||____
|||_|||_|_
|___||___|
|___|_||__
|_|||_||||
||___|||_|
|||||_|||_
||||||_|||
|||||__|||
|||_||_|__
|_||___|__
|__|______
|__|||_||_
|||___|||_
||_|__|_|_
|____||_||
||___||__|
|||_|||||_
|__|_|||__
|__|||||||
|__|_|_|__
|||__||__|
|_|_|_|_||
|_____||__
|||_||||||
|_|___|__|
|_|___|||_
|_|||__|_|
||____|___
|_____|_|_

stdout

5
7
1
1
8
2
8
9
5
6
3
1
1
3
3
1
2
8
1
1
1
3
6
1
9
2
2
4
2
1

stderr

Traceback (most recent call last):
  File "/volume/CODE", line 1, in <module>
    while 1:s=input()+"a";print(s[:s.find("__")].count("|"))
EOFError: EOF when reading a line

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffcae597910 /* 7 vars */) = 0
12    execve("/usr/bin/python3", ["/usr/bin/python3", "/volume/CODE"], 0x55e951267d50 /* 7 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x55e951267d38 /* 7 vars */) = 0
11    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=11, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
12    +++ exited with 1 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=12, si_uid=0, si_status=1, si_utime=1, si_stime=0} ---
10    +++ exited with 1 +++