#!/usr/bin/perl

use strict;
use warnings;

my @array = (1,5,6,7,8,55,63,77,89,103,104,105,106,200,215,554);
my %free_numbers = map {$_ => 1} @array;

for my $number (@array)
{
    my $ok = 1;
    for (my $i = 0; $i < 4; $i++)
    {
        if (! exists $free_numbers{$number + $i})
        {
            $ok = 0;
            last;
        }
    }
    if ($ok)
    {
        print "found consecutive numbers: ";
        for (my $i = 0; $i < 4; $i++)
        {
            print $number + $i, " ";
            delete $free_numbers{$number + $i};
        }
        print "\n";
    }
}

__END__
found consecutive numbers: 5 6 7 8 
found consecutive numbers: 103 104 105 106