I ran the following quick Benchmark code to test:
#!/usr/bin/perl -w
use strict;
use Benchmark;

my $input = 'X' x 65;  #test input
my @result;

timethese(-10, {
   'Regex' => sub {
                   @result = ($input =~ /(.{16})(.{20})(.{20})(.{1})(.
+{8})/);
               #    print join "\t", @result;
                  },
   'Unpack' => sub {
                   @result = unpack "A16A20A20AA8",$input;
               #    print join "\t", @result;
               },
});

[download]
which yielded: 
Benchmark: running Regex, Unpack, each for at least 10 CPU seconds...
     Regex:  9 wallclock secs (10.44 usr +  0.00 sys = 0.44 CPU) @ 198
+59.10/s (n=207329)
    Unpack: 11 wallclock secs (10.17 usr +  0.00 sys = 0.17 CPU) @ 333
+12.29/s (n=338786)

[download]

It would seem unpack is more efficient in this case.
-ase

In reply to Re: Fixed-Length Fields Question by ase
in thread Fixed-Length Fields Question by mrmick

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