#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my @array = ("M94202", "M94150", "M94297", "M94150", "M94161", "M94161", "M94162");

my $z = 1;

foreach my $item (@array) {
    if ($item =~ m/M/g) {
        my $uniqitem = $item;
        foreach $uniqitem (@array) {
            $uniqitem =~ s/$uniqitem/$z/g;
            $z = $z +2;
        }
    }
}
print Dumper \@array;
print "\n";