perl, 35 bytes

Result

AC

Duration

721ms

Code [DL]

#!perl -p
$t=$_|=$t;1while s/k /kk/

stdin

                 T                                
                                                  
              K                                   

stdout

                 T                                
                 t                                
              kkkt                                

stderr

strace

11    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7fff724b29f0 /* 7 vars */) = 0
13    execve("/usr/bin/perl", ["/usr/bin/perl", "/volume/CODE"], 0x5560223fad40 /* 7 vars */ <unfinished ...>
12    execve("/bin/cat", ["cat", "-"], 0x5560223fad30 /* 7 vars */) = 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} ---
13    <... execve resumed> )            = 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 +++