I can't think of a way to do what you want (may be other can), but personaly, I would put the whole body of the loop into a subroutine, then do

while (defined($line=shift @values)) {
   process($line);
}
while (defined($line=<$filehandle>)) {
   process($line);
}
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(The reason for keeping the body of the loop in the subroutine is that that way you will be sure you only need to make any changes in one place.