if (/\-+ [A-Za-z]{3} (.*?) (.*?) (.*?)\:(.*?)\:(.*?) (\d+)::(\d+)::Launching the JVM with following options/) {
    ...

##</code><code>##

# Declaration
my $m = 1;
my %MONTH = map { $_ => $m++ } qw( Jan Feb Mar Apr May ... );

# Later in the code:
$month = sprintf '%02d', $MONTH{$1};