i don't know what you mean by combined either, but perhaps:

open FILE1, "what.txt" or die "can't open what.txt : $!\n";
open FILE2, "what1.txt" or die "can't open what1.txt : $!\n";
while ($first = <FILE1> and $second = <FILE2>)
{
   #combine strings somehow
   #push onto an array
}
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