Hello gbwien,

Maybe this is not the best solution to your problem but it could be a point of start:

#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';

open (my $fhIn, '<', "in.txt")
    or die "Can not open 'in.txt': $!";

open (my $fhOut, '>', "out.txt")
    or die "Can not open 'out.txt': $!";

my %hash;
my $count = 0;
while (<$fhIn>) {
    chomp;
    if (/<SUBBEGIN/) {
    $count = 1;
    }
    elsif (/<SUBEND/) {
    $count = 0;
    }
    elsif ($count) {
    my @tmp = split /=/;
    chop $tmp[1];
    if (/MSISDN/) {
        $hash{MSISDN} = $tmp[1];
    }
    elsif (/ODBIC/) {
        $hash{ODBIC} = $tmp[1];
    }
    elsif (/ODBOC/) {
        $hash{ODBOC} = $tmp[1];
    }
    }
    if ($count == 0) {
    if (exists $hash{MSISDN}) {
        say $fhOut "Update Command <".$hash{MSISDN}.">,".$hash{ODBIC}.
+",".$hash{ODBOC}."";
    }
    else {
        say $fhOut "Update Command MSISDN=notSet,".$hash{ODBIC}.",".$h
+ash{ODBOC}."";
    }
    delete $hash{MSISDN};
    delete $hash{ODBIC};
    delete $hash{ODBOC};
    }
}

close ($fhIn)
    or warn "Could not close 'in.txt': $!";
close ($fhOut)
    or warn "Could not close 'out.txt': $!";

__END__

$ cat out.txt
Update Command <123476789678>,BIC,BAOC
Update Command MSISDN=notSet,BIC,BAOC
[download]

If there is something that you can not understand let me know. Maybe you will find other ways to approach your problem at Getting lines in a file between two patterns.

Hope this helps, BR.