I can't cope with your code - blame it on Rio - code tags notwithstanding and I don't believe it would run at all without compilation errors, but I do see some definite holes I can categorise...

my $matches = grep ... foreach ( @matches ) { ...
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should be my @matches. // are pattern match delimiters but the enclosed expression is not likely to be accepted as a pattern. Perhaps you could tell us what strings in the logfile you are trying to detect.