$sentence=~ s/\s//igs;

##</code><code>##

my @four=$sentence=~ /[a-zA-Z]{4}/igs; # Line 9 

##</code><code>##

   my $length=length($word);

##</code><code>##

unless (open(RESULT,">$output")){

##</code><code>##

} until ( my $word=~ /^.*$/); # Line 22  

##</code><code>##

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

## To chop a sentence at intervals of 4-letter and to print results:

my $sentence = "BEAR CALF DEER FEAR GEAR HEAR";
## To remove blank spaces
$sentence =~ s/\s//g;

my $output="Words .txt";
open RESULT, '>', $output or do {
    print "Cannot open file \"$output\".because: $!";
    exit;
    };

print "\n Words are:  \n";

foreach my $word ( $sentence =~ /[a-zA-Z]{4}/g ) {
    print"\n $word: ";
    print"\n Length of the word = 4\n\n";
    print RESULT "\n Words are:  \n
 Word: $word; Length of the word = 4\n\n";
    }
close RESULT;