I tried your solution. Here is my code which seems to work.

#!/usr/bin/perl

use strict;
use warnings;

my $in_file_name = "D:/temp.s3";
my $data = "";  

&extractDataFromSrecFile($in_file_name, \$data);
print($data,"\n");

sub extractDataFromSrecFile
{
    my ($file_name, $ref_data) = @_;
    my @in_data;


    # read file into memory
    open(my $fh, "<", $file_name) || die "Could not open \"$file_name\
+"";
        
    while( my $srec = <$fh> )
    {        
        chomp($srec);

        my $id = substr($srec,0,2);
        my $address = substr($srec, 4, 8);
        
        if( ($id eq "S3") &&
            ($address ne "FC000000") )
        {
            push(@in_data, $srec);
        }
    }

    close( $fh );

    
    # store sorted data and check if it is complete
    $$ref_data = "";
    my $next_address = 0xFC000018; # start address
    for( sort{ hex(substr($a, 4, 8)) <=> hex(substr($b, 4, 8)) } @in_d
+ata )
    {
        my $srec = $_;
        my $address = hex(substr($srec, 4, 8));
        my $nb_data_bytes = hex(substr($srec,2,2)) - 4 - 1;

        # completeness check
        if( $address != $next_address )
        {
            $$ref_data = "";
            print "ERROR: S3-Record with address " . sprintf("%08X", $
+next_address) . " is missing in input file!\n";
            return; 
        }
        
        $$ref_data .= substr($srec, 12, ($nb_data_bytes * 2));

        $next_address = $address + $nb_data_bytes;
    }
}
[download]

Because I want to learn feel free to improve the code and give hints what I could do better.

Thank you

Dirk