unless $seen{"$team$player"}++;

One small nit. Because the  %seen uniqification hash is common to all teams, it's possible to confuse certain team/player records, e.g.:
    Team    Player
    ABC     DEFGH
    ABCD    EFGH
which both become the key 'ABCDEFGH'.

This is easily avoided by joining the two strings with some character or character sequence that (you hope!) cannot possibly occur in team or player names:
    unless $seen{"$team\x00$player"}++;
(Update: Actually, for the given order of concatenation, it's only necessary that the separator character or character sequence cannot appear in the team name.)

This nit is very unlikely to bite, but may be very difficult to debug (or even see in large data sets) if it does.

Update: Another, possibly more significant nit. All team and player name data in the OPed example is uppercase. If there may be any mixing of case, then, e.g., 'Rose' will be distinct from 'ROSE' and de-duplication may fail. In this case, or even as a general precaution, team/player names can be common-cased:
    unless $seen{"\U$team\x00$player"}++;
See Quote and Quote-like Operators in perlop for  \U \L et al.

Give a man a fish:  <%-{-{-{-<

In reply to Re^2: Unique Values within AOH (updated) by AnomalousMonk
in thread Unique Values within AOH by dirtdog

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