perl script works as tree command, recursive call

this has been 5 years old, but to keep it.
if any suggestions or security hole, please share them.

tree.pl

# ! /usr/bin/perl

# use strict;
# use warnings;

###########################
# same as Windows NT tree #
###########################

$dir = `pwd`;
print $dir;
$dep = 1;
&dirproc($dep);

sub dirproc {
    # localize values, cz it's recursive sub-routine.
    my($dep) = @_;
    my(@files, $file);

    # get all files in the current directry.
    @files = sort(glob("*"));

    # show all files in the current directry.
    foreach $file (@files){
        if (-f $file){
            for ($i = 1; $i <= $dep; $i++){
                print "|\t";
            }
            print $file."\n";
        }
    }

    # show all directry in the current directry.
    # if directry, calls dirproc again.
    foreach $file (@files){
        if(-d $file){
            for ($i = 1; $i <= $dep; $i++){
                print "|\t";
            }
            print $file."\n";
            ++$dep;
            chdir($file);
            &dirproc($dep);
            chdir("..") or die "abort, maybe your environment is lack of memory.";
            --$dep;
        }
    }
}