Process common chunks of a sorted input stream

gistfile1.pl

#!/usr/bin/env perl

use strict;
use warnings FATAL => 'all';

my ( $key, @values ) = next_record();

while ( defined $key ) {
    my ( $next_key, @next_values ) = next_record();    
    if ( defined $next_key and $next_key eq $key ) {
        push @values, @next_values;
    }
    else {
        print join( "\t", $key, @values ) . "\n";
        $key = $next_key;
        @values = @next_values;
    }    
}

sub next_record {
    defined( local $_ = <> ) or return;
    chomp; split;
}