in reply to Where can I find more examples of use of Special Backtracking Control Verbs?

I usually use '(*FAIL)' with '(?{})' to generate all possible substrings of the string, or in similar cases. E.g.
    my $string = <>;
    my %substrings;
    $string =~ /(.+)(?{ $substrings{ $1 } = 1 })(*FAIL)/;

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E.g. to calculate some statistics: 
    / (\b\d+\b) .*? (\b\d+\b) (?{ $count += $1 > $2 }) (*FAIL) /x;

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But have no experience of using PRUNE, SKIP and others :)

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Re^2: Where can I find more examples of use of Special Backtracking Control Verbs?
by rsFalse (Chaplain) on Nov 07, 2018 at 12:30 UTC
    Also once I used '(?{})' with '(*FAIL)' simply for traversing all characters of the string.
        /.(?{ do_smth( $& ) })(*FAIL)/ for @lines;

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    This part: 
        /.(?{ do_smth( $& ) })(*FAIL)/

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    is similar to: 
        do_smth( $& ) while /./g;

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    , but it can not(?) be combined with 'for' into one short expression like: 
        do_smth( $& ) while /./g for @lines;  # syntax error

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    Instead I should write: 
        do{ do_smth( $& ) while /./g } for @lines;

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    Another variant here was to concatenate all lines: my $concatenated_lines = join $some_concatenator, @lines. And then simply match. But imagine if the regex is more complex and can accidentally match a concatenator as well.
    And another alternative here was to use eval within non-destructive substitution: 
        s/./ do_smth( $& ) /ger for @lines;

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    Note modifiers: e - for eval, and r - for non-destructiveness.
    But imagine do_smth function returning long strings (e.g. ( ( ord $& ) % 2 ? $odds : $evens ) .= $&) and it could possibly(?) slow down process.
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