If you prefer not changing your filehandle, you can also cat (or perhaps echo, if you're stuck in Windows land) a file into your script:

#!/usr/bin/perl -w

use strict;

print while (<STDIN>);
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Well, the keyboard is usually read using <STDIN> which is just another filehandle.

So say you have written a script that asks a few questions like:

print "What is your name? ";
my $name = <STDIN>; chomp $name;

print "What is your quest? ";
my $quest = <STDIN>; chomp $quest;

print "What is your favorite color? ";
my $color = <STDIN>; chomp $color;
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Anonymous Monk
I seek the Wisdom of the Monastery
Yellow...no, Blue! arghhhhhhhh!
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That allows you to alias STDIN to FOO and the file will be read instead of the keyboard while you are testing your program. When you're done testing, just remove the open statement and the *STDIN = *FOO line and you're all set.

Depends on what you mean by "simulate". One way to mean it is to force a "y\n" into your own tty input buffer, like so:

sub jam {
    $TIOCSTI = 0x80017472;
    for (split(//, $_[0])) {
        ioctl(STDERR, $TIOCSTI, $_) || die "bad TIOCSTI: $!";
    } 
}

jam("y\n");
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From the Perl Cookbook "solution" at www.perl.com:

    require 'sys/ioctl.ph';
    die "no TIOCSTI" unless defined &TIOCSTI;
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    Since sys/ioctl.h translation is so dodgy, you'll
    probably have to run this C program to get your
    TIOCSTI value.

        % cat > tio.c <<EOF && cc tio.c && a.out
        main() { printf("%#08x\n", TIOCSTI); }
        EOF
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