#!/usr/bin/perl

use strict;
use warnings;

open my $fh, '<', "input.txt"
  or die "Can't open the file: $!";

my @words;

for my $line (<$fh>){
    chomp $line;
    for my $word (split(/\s+/, $line)){
        if ($word =~ /[b-df-hj-np-tv-z]{4}/i){
            push @words, $word;
        }
    }
}

print "$_\n" for @words;