#!/usr/local/bin/perl -w
use strict;

my @attr_list = qw/ cn fonDeptName telephoneNumber l st
                    fonManagerDN=cn /;

# did you open the file?
open LDAPFILE, ">ldap" or die "Can not create ldap";

# print column header
print LDAPFILE "InputValue:", join(':', @attr_list), "\n";
close LDAPFILE;

# ...

# Set up a search pattern that will recognize any attribute.
my $attrs = join '|', @attr_list;  # <-- you probably want | instead of : ?

# Create a hash with attribute names as search keys
my %attrs = map { $_ => '' } @attr_list;

# ...
# ...