XOR_portmap file is as follows
m : XOR2 port map (A=> in1, B=> enable_c, Y => output);

##</code><code>##

uut_names file is as follows
M1
M2
M3

##</code><code>##

nets file is as follows
a_c
b_c
c_c

##</code><code>##

enabled_nets file is as follows
a_e
b_e
c_e

##</code><code>##

use strict;
use warnings;

open (IN1, "<XOR_portmap.txt") or die;
open (IN2, "<uut_names.txt") or die;
open (IN3, "<nets.txt") or die;
open (IN4, "<enabled_nets.txt") or die;
open (OUT, ">>XOR_portmap_nets.txt") or die;

my @uut_names = <IN2>;
my @nets = <IN3>;
my @enabled_nets = <IN4>;

chomp @uut_names;
chomp @nets;
chomp @enabled_nets;

while (<IN1>) {
    foreach my $i ( 0..$#nets ) {
        print OUT if ((s/m/$uut_names[$i]/) && (s/in1/$nets[$i]/) && (
+s/output/$enabled_nets[$i]/));
    }
}

close (IN1);
close (IN2);
close (IN3);
close (IN4);
close (OUT);

##</code><code>##

M1
 : XOR2 port map (A=> a_c
, B=> enable_c, Y => a_e
);

##</code><code>##

M1 : XOR2 port map (A=> a_c, B=> enable_c, Y => a_e);
M2 : XOR2 port map (A=> b_c, B=> enable_c, Y => b_e);
M3 : XOR2 port map (A=> c_c, B=> enable_c, Y => c_e);