#!/usr/bin/perl

use strict;
use warnings;

my $S = 'Hello World 123456 !!! 789 ...';
my $P = 14;   # $P points to digit '3'

# I want to capture 123456 but I can only capture 3456 with this regex:

my $INT = ($S =~ m/^.{$P}(\d+)/) ? $1 : '';

print "\n :$INT: \n";