Another way, avoiding any sorting:

use strict;
use warnings;
use 5.010;

my @month_names = ( qw /
  January February March April May June July
  August September October November December
/ );

my %month_hash;
while ( my $line = <DATA> ) {
  $month_hash{$_} = 1 for split /[^a-z]+/i, $line;
}

for ( @month_names ) {
  say if $month_hash{$_};
}

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