m4, 70 bytes

Result

INVALID

Duration

697ms

Code [DL]

m4wrap(`syscmd(`sed "1h
\${:1
x
s/ \$//
t1
x
:2
s/K /KK/
t2
h
}
g"')')

stdin

                    T                             
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                K                                 

stdout

                    T                             
                    T                             
                    T                             
                    T                             
                    T                             
                    T                             
                    T                             
                    T                             
                    T                             
                    T                             
                KKKKK

stderr

strace

11    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffed5dba3a0 /* 7 vars */) = 0
12    execve("/bin/cat", ["cat", "-"], 0x55f2eef0bd30 /* 7 vars */ <unfinished ...>
13    execve("/usr/bin/m4", ["/usr/bin/m4", "/volume/CODE"], 0x55f2eef0bd40 /* 7 vars */ <unfinished ...>
12    <... execve resumed> )            = 0
13    <... execve resumed> )            = 0
12    +++ exited with 0 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=12, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
14    execve("/bin/sh", ["sh", "-c", "sed \"1h\n\\${:1\nx\ns/ \\$//\nt1\nx\n:2\n"...], 0x7ffc22f1baa0 /* 7 vars */) = 0
14    execve("/bin/sed", ["sed", "1h\n${:1\nx\ns/ $//\nt1\nx\n:2\ns/K /KK"...], 0x563b37a3ad20 /* 7 vars */) = 0
14    +++ exited with 0 +++
13    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=14, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
13    +++ exited with 0 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=13, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
11    +++ exited with 0 +++