#!/usr/bin/perl

use strict;
use List::Vectorize;

open F, $ARGV[0] or die "cannot open $ARGV[0]";
my $fun = $ARGV[1] ? $ARGV[1] : 'sub {$_}';
if($fun !~/^\s*sub\s*\{/) {
	$fun = "sub $fun";
}
$fun =~s/\$_(?!\[)/\$_\[0\]/g;
$fun = eval($fun);
if ($@) {
	print "applying function format is wrong.\n";
	exit;
}
my $a = [ <F> ];
$a = sapply($a, sub {chomp $_[0]; $_[0]});
print join "\n", @{subset($a, $fun)};
print "\n";