# extract_min_uniq_2.pl                                     15jun15waw


use warnings;
use strict;

use LeadingDistinct;

use Data::Dump qw(dd);

use constant DEBUGGING => 0;
use constant {
    PR_DB1 => 1 && DEBUGGING,
    PR_DB2 => 1 && DEBUGGING,
    PR_DB3 => 1 && DEBUGGING,
    };

my @tokens = qw/report_time report_day reset read/;

my %min_distinct = LeadingDistinct::extract(@tokens);
dd \%min_distinct if PR_DB1;

for my $k (keys %min_distinct) {
    $min_distinct{$k} = max_optional_rx($k, $min_distinct{$k});
    }
dd \%min_distinct if PR_DB2;

my ($find) =
    map qr{ (?<! [[:alpha:]_]) (?: $_) (?! [[:alpha:]_]) }xms,
    join '|',
    values %min_distinct
    ;
dd $find if PR_DB3;

while (<DATA>) {
    next unless m{ \A ($find) }xms;
    print "$1 \n";
    }


# subroutines ######################################################

sub max_optional_rx {

    my ($whole,   # full word
        $unique,  # distinctive characters at start of word
        ) = @_;

    my @tail = split //, substr $whole, length $unique;
    my $opt_tail = optional_tail(@tail);

    return qr{ \Q$unique\E $opt_tail }xms;

    }

sub optional_tail {

    my $rx = '';
    return $rx unless @_;

    $rx = quotemeta shift @_;
    for my $c (@_) {
        $c = quotemeta $c;
        $rx .= " (?: $c)?";
        }

    $rx = qr{ $rx }xms;
    return "$rx?";

    }


__DATA__
report_t
  14:09:33 PDT
report_d
Fri Jun 12 2015
report (should not show up)

res
Resetting the time

report_time
  00:00:00

rea foo.bar
Info: reading file foo.bar