#!/usr/bin/perl -w

opendir(DIR, ".");
@files = grep(/\.txt$/,readdir(DIR));
closedir(DIR);

open(F,'>done.txt');

foreach $file ( @files ) {
  open(A,$file);
  @a=<A>;
  close(A);
  print F @a;
  print F "\n";
  }
close(F);
print "Done.\n";

$ perlcc -o union union.pl
pcc7Uag4.c: In function `perl_init_aaaa':
pcc7Uag4.c:1051: warning: this decimal constant is unsigned only in ISO C90
Info: resolving _PL_ppaddr by linking to __imp__PL_ppaddr (auto-import)
Info: resolving _MallocCfg_ptr by linking to __imp__MallocCfg_ptr (auto-import)

$ ./union
Done.

First

Something Else

First
Something Else