sub findString($) {
    my $line = shift;
    print "found\n" if $line =~ eval "qr/$regex/";
}

##</code><code>##

my $s = 'Tue Feb  8 11:11:11 2005: blah blah blah';

my ($wday, $mon, $mday, $year);

my $regex = qr/^(??{$wday}) (??{$mon})\s+(??{$mday}) \d{2}:\d{2}:\d{2} (??{$year}):/;
$wday = 'Tue';
$mon = 'Feb';
$mday = '8';
$year = '2005';

sub findString;
findString($s);

sub findString($) {
    my $line = shift;

    print "found\n" if $line =~ /$regex/;
}