#! / usr/bin/perl
use warnings;
use strict;
use Mail::RFC822::Address ();

my $filename = "irgendwas.txt";
unless (open (FH, $filename)) {
  die "Error in opening '$filename': $!
";
}
else {
  while (<FH>) {
    chomp($_);
    foreach my $word ( split(/\s+/, $_) ) {
      if (&Mail::RFC822::Address::valid($word)) {
        print "$word
"; # oder mach sonst was mit $word
      } # if
    } # foreach
  } # while
  close (FH);
} # else