my %severity_map = (
     "Error"                    => "Warning",
     "Critical"                 => "Critical",
     "System Shutdown"          => "Fatal",
     "Failure"                  => "Critical",
     "Uncorrectable ECC"        => "Fatal",
     "Warning"                  => "Minor",
     "Alarm"                    => "Critical",
     "System Powered Off"       => "Fatal",
     "Memory Bank Deconfigured" => "Warning"
);

my @description_samples = (
    "Memory Bank Deconfigured",
    "Uncorrectable ECC",
    "Sticky Corrected ECC Error",
    "System Shutdown"
);

my $keywords = join "|" => map quotemeta, keys %severity_map; 

for (@description_samples) {
    my $severity = "Warning";

    /($keywords)/i
        ? $severity = $severity_map{$1}
        : print "Can't find severity mapping for: $_, using default\n";

    print "$_ has severity $severity\n";
}