Given that your password file is fairly small, I would suggest reading in the entire file and storing the results in a hash. You could then go over your second file, line by line to save memory, and sub in the passwords with a regular expression. Something like:

#!/usr/bin/perl
use strict;
use warnings;

open my $pass_handle, '<', 'passwords.txt' or die "Open fail: $!";
my %password;
while (<$pass_handle>) {
    chomp;
    my ($key,$pass) = split;
    $password{$key} = $pass;
}

open my $input_handle, '<', 'input.txt' or die "Open fail: $!";
open my $output_handle, '>', 'output.txt' or die "Open fail: $!";
while (<$input_handle>) {
    s/^(\S+\s+\S+\s+".*"\s+\S+\s+\S+\s+)(\S+)(\/)/$1$2$3$password{$2}/
+;
    print $output_handle $_;
}
[download]

That regular expression is likely much uglier than it needs to be, but I really have no idea how your actual input is formatted. Note that I use the special variable $_ extensively.

That might not do the right thing if $2 isn't a key in the hash, also.

True, but it will do no harm and will emit a warning (unitialized value) with the correct input file line number, which is usually as much as you can hope for in this case.

Baww, i weep for you, must be really hard to keep that going since march