DouKaku?

#!/usr/local/bin/perl
use strict;
use warnings;
use Regexp::Assemble;

my $ra = Regexp::Assemble->new;
while(<>){
    chomp;
    next unless $_;
    $ra->add($_);
}
print $ra->re, "\n"
__END__

% grep program /usr/share/dict/words 
program
programist
programistic
programma
programmar
programmatic
programmatically
programmatist
programmer

% grep program /usr/share/dict/words | perl sample.pl 
(?-xism:program(?:m(?:a(?:ti(?:c(?:ally)?|st)|r)?|er)|ist(?:ic)?)?)

import sys

def get_chr_tree(strs, before=""):
  index = len(before)
  s = set([str[index] for str in strs if len(str) > index and str[:index]==before])
  l = [get_chr_tree(strs, before+c) for c in s]
  return [before[-1]] + l if before else l[0]

def merge_chr(chr_tree):
  try:
    if len(chr_tree) == 2:
      return merge_chr([chr_tree[0]+chr_tree[1][0]] + chr_tree[1][1:])
    else: return [chr_tree[0]] + [merge_chr(tree) for tree in chr_tree[1:]]
  except IndexError:
    return chr_tree

def to_regexp(chr_tree):
  def make_regexp(chr_tree):
    if len(chr_tree) == 1: return chr_tree[0]
    else:
      hatena = "?" if [True for l in chr_tree[1:] if "\n" in l] else ""
      try:
        inner = "".join(["|" + make_regexp(tree) for tree in chr_tree[1:]])
      except IndexError:
        print "IndexError",chr_tree
        inner = ""
      return chr_tree[0] + "(?:" + inner + ")" + hatena

  return "(?-xism:" + make_regexp(chr_tree).replace("|\n", "").replace("\n", "").replace(":|", ":") + ")"

words = []
for line in sys.stdin: words.append(line)
chr_tree = get_chr_tree(words)
merged_chr_tree = merge_chr(chr_tree)
print to_regexp(merged_chr_tree) # => (?-xism:program(?:m(?:a(?:ti(?:c(?:ally)?|st)|r)?|er)|ist(?:ic)?)?)