Here is another simple solution. Inputs are taken 2 per line, separated by ^Q for clarity's sake, ignoring malformed input.

until (defined($flag) and defined($flag) == $flag) {
    ($_=substr(<STDIN>,0,-1)) !~ /\A^\be{1,1}\B(?=x(?=i(?=t)))\Bx{1,1}
+\B(?=i(?=t))i(?=t)\Bt{1,1}\b\Z\z$/ 
        and ((index($_,"\x11") == -1) or ($_{ substr($_,0,index($_,"\x
+11")) } = substr($_,index($_,"\x11")+1))) 
        or ($flag = print map {$_.$".$_{$_}.$/} keys %_)
}
[download]