use strict;
use warnings;

opendir my $scanDir, $directory or die "Unable to open directory $directory: $!\n"
my @files = grep /^R/, readdir $scanDir;
closedir $scanDir;

for my $filename (@files) {
    open my $inFile, '<', "$directory/$filename" or die "Can't open $directory/$filename: $!";
    ...
    close $inFile;
}