#! perl
use strict;
use warnings;

my $in_file = 'input.txt';
my %out_files;

open(my $in, '<', $in_file)
    or die "Cannot open file '$in_file' for reading: $!";

while (my $line = <$in>)
{
    my ($datum, $type) = split ' ', $line;

    unless (exists $out_files{$type})
    {
        my $filename = $in_file . $type . '.txt';

        open(my $fh, '>>', $filename)
            or die "Cannot open file '$filename' for appending: $!";

        $out_files{$type} = $fh;
    }

    print { $out_files{$type} } $datum . "\n";
}

for (keys %out_files)
{
    close $out_files{$_}
        or die "Cannot close the '$out_files{$_}' output file: $!";
}

close $in
    or die "Cannot close file '$in_file': $!";