my $directory = "/home/e/Doc/AutoMation";

chdir $directory;
opendir( DIR, "." );

for my $file ( readdir DIR ) {
    next unless -f $file;
    open( my $in_fh, '<', $file );
    …
}

##</code><code>##

opendir( DIR, $directory );
for my $file ( readdir DIR ) {
    next unless -f "$directory/$file";
    open( my $in_fh, '<', "$directory/$file" );
    …
}