All my comments are in the.. uh, comments. In the code. *grin*

#***********************
# Perl ActiveX Script
#***********************
use Win32; #allows for MsgBox functionality
use strict; ## <---- get in the habit <-----

## "die MsgBox()" works, but it's more of a coincidence;
## this is better
sub msgbox_die {
    my $problem = shift;
    MsgBox $problem;
    die $problem;
}

******************************************

sub Main()
{
my $file1 = "c:/foo/sub_list.txt"; 
my $file2 = "c:/foo/cust_names_city.txt";
## you don't want the > in the filename - just a matter of cleanliness
my $file3 = "c:/foo/cust_names_city_new.txt";

my @search;
my @replace;

open (SUBLIST, $file1) || msgbox_die("Can't open file");
## fetch only one line at a time rather than slurping the entire file 
+at once
while(<SUBLIST>) {
    ## use a third parameter in split:
    ## specifies how in how many parts we want to break the string
    ## split() can quit looking after that number,
    ## and it also prevents loss of data
    my ($key,$value) = split (/=/, $_, 2);
    chomp ($value);
    push @search, qx/\b\Q$key/; ## put a precompiled regex in the arra
+y
    push @replace, $value;
}
close (SUBLIST);
 
open(CUSTLIST, $file2) || msgbox_die("Can't open file");
open(NEWCUSTLIST, ">$file3") || msgbox_die("Can't open file"); ## you 
+want the > here
while(<CUSTLIST>) { ## ditto slurping
    my $i = 0;
    for my $re (@search) { ## go through all the stored regexes,
        s/$re/$replace[$i]/ig; ## and apply them,
        $i++; ## keeping track of which string we are replacing with
    }
    print NEWCUSTLIST $_; ## no need to keep the result in memory

}
close (CUSTLIST);
close (NEWCUSTLIST);

return 0;     # DTSTaskExecResult_Success;
}

******************************************
[download]

____________
Makeshifts last the longest.