use strict;
use warnings;

##</code><code>##

use File::Slurp qw( read_file );
my $projectA = read_file('projecta.txt');
my $projectB = read_file('projectb.txt');

##</code><code>##

sub read_file {
   my $filename = shift;

   # Force whole file into one scalar unless we want
   # each "line" on its own
   local $/ unless wantarray;

   open my $fh, '<', $filename # USE 3-args version of open!
      or die "open('$filename'): $!"; # verify your open!

   return <$fh>; # enjoy auto-close of $fh :)
}