#!/usr/bin/perl
# qnumcat - demo additive output filters

number();                   # push number filter on STDOUT
quote();                    # push quote filter on STDOUT

while (<>) {                # act like /bin/cat
    print;
} 

close STDOUT;               # tell kids we're done--politely
exit;

sub number {
    my $pid;
    return if $pid = open(STDOUT, "|-");
    die "cannot fork: $!" unless defined $pid;
    while (<STDIN>) { printf "%d: %s", $., $_ } 
    exit;
} 

sub quote {
    my $pid;
    return if $pid = open(STDOUT, "|-");
    die "cannot fork: $!" unless defined $pid;
    while (<STDIN>) { print "> $_" } 
    exit;
}