This is less than ideal, but it gives you a little better visibility than just line number.

{ my ($line,$occurrence) = (0,0);
sub some_sub {
    $, = ' - ';
    my @caller = caller();

    if($caller[2] == $line) {
        $occurrence++;
    }
    else {
        $line = $caller[2];
        $occurrence = 0;
    }
    print @caller, $occurrence, $/;
}
}
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You example shows the biggest limitation to this approach. $occurrence will just keep growing since it is the same line number. But if you know you are dealing with a specific number of calls on the line, you can mod whatever and get the specific occurence on the line.