use strict;
use warnings;
use diagnostics;
use Modern::Perl;
undef $/;
open my $FH, '<', '/home/james/andrew/Perl_file.txt' or die "Could not
+ open file= $!";

foreach(my $line =  <$FH>) {
    $line =~ s/\s+//gs;
    my $char_a = substr($line, 0, 2);
    my $char_b = substr($line,2,2);
    print $char_a;
    print $char_b;
}