Not to mention that it's really easy to add data validation with this approach:

use strict;
use warnings;

while(<DATA>){
    s/\A(.)(.{15})(.{14})(.{13})\Z/$1,$2,$3,$4/
        or die "bad record: '$_'";
    print;
    }

__DATA__
0123456789012345678901234567890123456789012
C4432882490H019000020150211ESL6690 0H2015PC
C4833076550HC0P0000201412093J46651 0H2015DX
C6033106980H057130020150323FRE7602 0H2015PC
C663160140MT007015G20141124274847A MT2015PC
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