Try this. I've assumed that you just wrapped the two lines for posting.

It's simpler and commented, which usually makes it more efficient and readable. Though the former is a matter of trial more than know-how and the latter is in the eye of the beholder.

my $re = qr|
    ( \S+ ) \s                    # Month $1
    ( \S+ ) \s                    # Day   $2
    ( \S+ ) [^\(]+                # Time  $3
    \( 
    ( [^@]+ )                     # User $4
    @ 
    ( [^\)]+ )                    # IP $5
    \) [^/]+
    ( .* )\sdownloaded\s\(        # File $6
    ( \d+ ) \D+                   # Size $7
    ( [^\)]+ )                    # Speed $8
|x;
[download]