use strict;
use warnings;

my @dates;
my $string = do {$/ = ""; <DATA>};

while ($string =~ /\b(\d{2})-(\d{2})-(\d{4})\sPerl\sParty/g)
  {
  push @dates, "$1\.$2\.$3";
  }

print join "\n", @dates;

__DATA__
All kinds of text 01-01-2003 Perl Party more text 01-01-2004 Perl Party
and even more text 01-01-2005 Perl Party
and finally some other date 01-01-2006