##
my $fh = $FH[$i];
while (my $line = <$fh>) {
...
}
##
##
open(FILE_A,">","a.txt") || ...;
open(FILE_B,">","b.txt") || ...;
my @FH=(*FILE_A,*FILE_B);
##
##
open(my $FILE_A,">","a.txt") || ...;
open(my $FILE_B,">","b.txt") || ...;
my @FH=($FILE_A,$FILE_B);