What have you tried? What didn't work? Demonstrated effort is generally appreciated around the monastery - see How do I post a question effectively?.

You could do this quite compactly using embedded Perl code in a regular expression, but given that you are a "complete novice", a simpler algorithm of wrapping a substitution in a while loop would likely be sufficient. I assume you know how to open files and print output, so I will give you a simple demonstration of how you might implement your algorithm using regular expressions. 

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

my $input = '0004$ADAM0002*330004%19770004$BOB 0002*430004%1967';

while( length $input ) {
    unless ($input =~ s/^(\d+)(.)//) {
        die "Input misformatted: $input";
    }
    my $len = $1;
    my $type = $2;

    unless ($input =~ s/^(.{$len})//) {
        die "Input misformatted: $len, $type, $input";
    }
    my $record = $1;
    
    print "Type:\t<$type>\nRecord:\t<$record>\n\n";
}

[download]

outputs: 

Type:   <$>
Record: <ADAM>

Type:   <*>
Record: <33>

Type:   <%>
Record: <1977>

Type:   <$>
Record: <BOB >

Type:   <*>
Record: <43>

Type:   <%>
Record: <1967>

[download]

If you have questions about how this works, I'd be happy to expound, though you should be able to find any answer in perlre and/or perlretut.

In reply to Re: Splitting file into separate files based on record lengths and identifiers by kennethk
in thread Splitting file into separate files based on record lengths and identifiers by monty77

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