for(<>){($a,$b,$c,$d,$e,$f)=/\d+/g;$a+=$d,$b+=$e,$c+=$f;$c>59&&($c%=60,$b++);$b>59&&($b%=60,$a++);$a>23and$a%=24;s/^(.)$/0$1/for$a,$b,$c;s/\n/=$a:$b:$c\n/;print}
Note that non-ascii characters in the above source code will be escaped (such as \x9f).