#!/usr/bin/perl
use warnings;
use strict;

my $file = 'oldcoffee.tmp';
my $out  = 'coffee.tmp';

open FILE, '<', $file or die "Can't open file $file! $!\n";

while ( <FILE> ) {
    if ( /^From / && /(\d{4})$/ ) {
        # Update: changed 'readonly' to 'append'
        open OUT, '>>', "$1$out" or die "Can't open $1$out! $!\n";
    }
    fileno OUT and print OUT;
}

close FILE or die "Can't close file $file! $!\n";

__END__