my $packed = pack "H*", sprintf "%07dC",  $num_records;
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Perl can count the records and add the trailer record, too, but I don't know what record format you're using.

Thanks, this worked perfectly...

pack doesn't support this directly. This will do the job, though it can probably be made significantly more efficient:

sub toComp3{ 
    my $num = shift; 
    my @digits = split'',abs $num; 
    unshift @digits, 0 unless @digits & 1;
    push @digits, $num < 0 ? 13: 12; 
    my $comp3 = ''; $comp3 .= chr( shift( @digits ) * 16 + shift( @dig
+its ) ) 
        while @digits; 
    return $comp3 
}

print unpack 'H*', toComp3( 240 );;
240c
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It also doesn't cover unsigned numbers. Though a flag to indicate signed-ness could be added.

There is a module, Convert::IBM390, that supports various conversion functions for data to/from a mainframe. One is packeb:

use Convert::IBM390 qw(packeb);
my $comp3 = packeb( 'p4', 240 );  #77 A  PIC S9(7) COMP-3.
print $comp3;
__END__
~~output~~
0x0000240c  (of course, in binary)
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It works well, and handles negative values.

Good luck. -c

You didn't do much research, did you?

pack, print, sprintf %04x, 123;