fish-shell-pure, 163 bytes

Result

AC

Duration

1327ms

Code [DL]

read s
set t (string length (string trim -r $s))
while read p
echo $s
set k (string trim -r $p)
[ $k ]&&echo $k(string repeat -n(math $t-(string length $k)) @)
end

stdin

                               T                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
                                                  
       K                                          

stdout

                               T                  
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                               T                  
       K@@@@@@@@@@@@@@@@@@@@@@@@

stderr

strace