use autodie;
use List::MoreUtils qw/uniq/;
open my $F1, $filename1;
open my $F2, $filename2;
my @files = unique
            map $_->[0],
            grep $_->[1] =~ /$variable/,
              (map [$filename1, $_] <$F1>),
              (map [$filename2, $_] <$F2>),
            ;