How about using hash with $USERNUM as key?
Instead this:

push(@Recs, "$USERNUM|$RECTYPE|$ASSET|$EXTK");
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Try this:

push(@{$Recs{$USERNUM}}, "$RECTYPE|$ASSET|$EXTK");
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Where Recs are defined somewhere above as my %Recs.
Then just go through hash and take all the records.

for my $USERNUM (keys %Recs)
{
  for my $rec (@{$Recs{$USERNUM}})
  {
    ($RECTYPE, $ASSET, $EXTK) = split /\|/, $rec;
    print "$USERNUM $RECTYPE $ASSET $EXTK\n";
  }
}
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Regards,