You probably haven't turned warnings on, as perl would've told you "Applying pattern match (m//) to @array will act on scalar(@array) at foo.pl line 17".

Your regex looks fine for what you want to do, but your while should be more like that:

while (<DATA>) {
    chomp;
    next unless /^(.*)(\d+:\d+:\d+)(.*?)$/;
    # if you're here, there was a match
    # do what you want with $1, $2 and $3
    ...
}
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