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

open my $fi, "<", "file.ini" or die "open error: $!";
open my $fo, ">", "file2.ini" or die "open for output error: $!";

while(<$fi>) {
        print $fo $_;
        if(/^ComPort=(\d+)/i)
        {
          print $fo "EnableUSB=" . ($1 > 10 ? 1 : 0) . "\n";
        }
}

close $fo;
close $fi;