If you don't want to destroy @values as you go along (as some of the above solutions do), you can make an iterator to return the appropriate "next thing":

my $iter = do {
  my $i;
  sub { $i < @values ? $values[$i++] : <$filehandle> }
};

while ( my $line = $iter->() ) {

  ## do stuff ...

}
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The readline on the filehandle is still not performed until needed and @values is kept intact.