Right, I wanted to suggest some state machine along this too:

#!/usr/bin/perl

use strict;
my @lines;

sub flush {
        return unless grep(/'Errors'/, @_);
        print "Got:\n\t", join ("\t", @_), "\n";
}

while (<>) {
        # trigger on last line of an error message
        flush(@lines,$_),@lines=(),next if m{^\s*\};\s*$}; 
        # triggger on next timestamp
        flush(@lines),   @lines=()      if m{^\s*\[\d\d\d\d\/};
        push(@lines, $_);
}
flush(@lines);
[download]

However, all solutions I have seen so far trigger evaluation with the next timestamp only. When using tail -f, the error will be processed only when the next log-line with a time-stamp is encountered - which might happen some hours or days later. IF seeing an error ASAP is important to the OP, the evaluation should be triggered additionally by matching for }; or by some timeout-mechanism, e.g. using alarm().
Update: final flush(...) added