package MatchRegex;

use strict;
use vars qw( @ISA @EXPORT_OK @digits @alpha );

require Exporter;
@ISA = 'Exporter';
@EXPORT_OK = qw( digits alpha UCalpha LCalpha );

@digits = (0..9);
@alpha = ('a'..'z', 'A'..'Z');

sub digits {
  ref $_[0] and local @digits = @{shift()};  # could use my()
  my $len;
  if (!@_) { $len = 1 }
  elsif (@_ == 1) { $len = $_[0] }
  else { $len = $_[0] + rand($_[1] + 1 - $_[0]) }
  return map $digits[rand @digits], 1 .. $len;
}

sub LCalpha { local @alpha = @alpha[0..25]; α }

sub UCalpha { local @alpha = @alpha[26..51]; α }

sub alpha {
  ref $_[0] and local @alpha = @{shift()};  # could use my()
  my $len;
  if (!@_) { $len = 1 }
  elsif (@_ == 1) { $len = $_[0] }
  else { $len = $_[0] + rand($_[1] + 1 - $_[0]) }
  return map $alpha[rand @alpha], 1 .. $len;
}

##</code><code>##

use MatchRegex qw( digits UCalpha );

$filename = join "", (
  digits(2),     # \d{2}
  UCalpha(2,5),  # [A-Z]{2,5}
  '_',           # _
  digits(2),     # \d{2}
  digits(2),     # \d{2}
  digits(4),     # \d{4}
);