#!usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my @final;
while (<>) { # Read all files that provided through ARGV
    chomp;
    my @tmp = split / /, $_;
    # print Dumper \@tmp;
    my $first = unpack 'a', $tmp[0];
    push @final, join(' ', $first, $tmp[2], $tmp[3]);
} continue {
    close ARGV if eof; # reset $. each file
}

print Dumper \@final;

__END__

$ perl test.pl in.txt
$VAR1 = [
          'A 1 violation',
          'A 4 violations',
          'B 3 violations'
        ];

__DATA__

A_01: xxxxxxxxxxxxxxxxxxxx......... 1 violation
A_02: xxxxxxxxxxxxxxxxxxxx......... 4 violations
B_02: xxxxxxxxxxxxxxxxxxxx......... 3 violations