Why would my if(-f ) not be working? - perl

Question

When initially checking if ARGV[0] is a file or directory, it worked fine with accurate results. Then further down into sub files I try it again and it doesnt return anything. This may seem like a small silly question but Im a student and help on programming on the weekends is scarce. Sometimes a new set of eyes can help.Thanks in advance.
#!/usr/bin/perl -w
my %hash;
my $args = #ARGV;
my $dh = $ARGV[0];
if ( -f $dh ) {
words($dh);
} elsif ( -d $dh ) {
files($dh);
}
sub words {
open( my $file, '<', $_[0] ) or die 'cant open file';
while ( my $line = <$file> ) {
chomp $line;
#words = split( /\s+/, $line );
foreach $word (#words) {
$word =~ tr/A-Z/a-z/;
$hash{$word}++;
}
}
foreach $key ( keys %hash ) {
print $key. " " . $hash{$key} . "\n";
}
}
sub files {
opendir( DH, $_[0] );
my #paths = grep !/^\./, readdir(DH);
closedir(DH);
foreach (#paths) {
if ( -f $_ ) {
print $_. "\n";
}
}
}

Answer 1

You're missing path to your file,
if (-f "$_[0]/$_") ..
or to make it less obscure,
sub files{
my ($path) = #_;
opendir(my $DH, $path);
my #paths = grep !/^\./, readdir($DH);
closedir($DH);
foreach (#paths) {
if (-f "$path/$_") {
print "$_\n";
}
}
}

Answer 2

As has already been stated, the return values of readdir contain just the basename. Therefore, to do file tests, you must either chdir or include the path info explicitly.
if (-f "$_[0]/$_") {
One alternative solution is to use Path::Class or some similar module for doing Cross-platform path specification manipulation.
The following is your script rewritten using this module:
use strict;
use warnings;
use Path::Class;
my $path = shift // die "Usage: $0 <Dir or File>\n";
words($path) if -f $path;
files($path) if -d $path;
sub words {
my $file = file(shift);
my %count;
$count{ lc($_) }++ for split ' ', $file->slurp;
for my $key ( keys %count ) {
printf "%s %s\n", $key, $count{$key};
}
}
sub files {
my $dir = dir(shift);
for ( $dir->children ) {
next if $_->is_dir;
print "$_\n", $_->basename;
}
}