use warnings;
use strict;

use Data::Dumper;

my %month_names = (
    January => 1,
    February => 2,
    March => 3,
    April => 4,
    May => 5,
    June => 6,
    July => 7,
    August => 8,
    September => 9,
    October => 10,
    November => 11,
    December => 12,
);

my @months;

while (<DATA>) {
    my ($client, $rest) = split /\|/;
    $rest =~ s/\s+//g;
    push @months, split /\d+/, $rest;
}

@months = uniq(@months);
@months = sort { $month_names{$a} <=> $month_names{$b} } @months;

print Dumper \@months;

sub uniq {
    my %seen;
    grep ! $seen{$_}++, @_;
}


__DATA__
IBM | February 1 March 5 July 4
Oracle| January 3 March 4 April 6 May 5
RedHat | March 2 June 3 August 1