use strict;
use warnings;

my %errors = (
    'input file not found' => sub {
        print "Bloody input file is missing!\n";
    },
    'signing key not found' => sub {
        print "meh, we're screwed!\n";
    },
    'no keys found' => sub {
        print "This doesn't need encrypting anyway...\n";
    }
);

my $program_output3 = '3001:input file not found';

chomp $program_output3;           # chomp any newline
$program_output3 =~ s/^\d+://;    # remove the digits/colon

$errors{lc $program_output3}->(); # lowercase, just in case

##</code><code>##

Bloody input file is missing!