my @files = map { my $s = $_; $s =~ s/^\s+//; $s =~ s/\+s$//; $s }
            <$FILES>;

##</code><code>##

my @files = map { my $s = $_; for ($s) { s/^\s+//; s/\+s$//; } $s }
            <$FILES>;

##</code><code>##

my @files = <$FILES>;
for (@files) { s/^\s+//; s/\+s$//; }

##</code><code>##

use List::MoreUtils qw( apply );
my @files = apply { s/^\s+//; s/\+s$//; } <$FILES>;

##</code><code>##

use Algorithm::Loops qw( Filter );
my @files = Filter { s/^\s+//; s/\+s$//; } <$FILES>;

##</code><code>##

while (<$FILES>) {
   s/^\s+//; s/\+s$//;
   ...
}