#!/usr/bin/perl

# http://perlmonks.org/?node_id=1207332

use strict;
use warnings;

my @grid =
(
    [ qw( a a b a c ) ],
    [ qw( a a a c f ) ],
    [ qw( a f c 1 b ) ],
    [ qw( a w x c z ) ],
    [ qw( a q q q c ) ],
);

$_ = join '', map join('', @$_) . "\n", @grid; # convert to string
print;

recognize( pattern => 'horizontal', min => 3 );
recognize( pattern => 'vertical',   min => 5 );
recognize( pattern => 'diagonal',   min => 2 );

sub recognize
  {
  my %args = @_;
  my ( $direction, $min) = @args{ qw( pattern min ) };
  $min // die "min not defined";
  my $reps = $min - 1;
  my $linesize = /\n/ && $+[0];
  my $gapref = { horizontal => [0], vertical => [$linesize - 1],
    diagonal => [$linesize - 2, $linesize]}->{$direction} //
    die "invalid direction $direction";

  for my $gap ( @$gapref )
    {
    print "\n";
    print "$direction @{[ 1 + length($2) / ($gap + 1) ]} '$1' at ",
      $-[1] % $linesize, ' ', int $-[1] / $linesize, "\n"
      while /(\w)(?=((?:.{$gap}\1){$reps,}))/gs;
    }
  }