my @values = qw(Stuff you want to pass in);
print "Some question\n";
chomp(my $file = <>);
if ($file eq 'A') {
    do_A($file, @values);
} elsif ($file eq 'B') {
    do_B($file, @values);
} elsif ... {
} else {
    complain_that_value_sucks($file, @values);
}
[download]

Now, that's a really piss-poor thing, especially if you have more than 5-10 options. So, we can use a dispatch table. This is a preferred method of doing things.

my %dispatch_table = (
    A => \&do_A,
    B => \&do_B,
    C => \&do_C,
);

my @values = qw(Stuff you want to pass in);

print "Some question\n";
chomp(my $file = <>);

my $sub = $dispatch_table{$file} || \&complain_that_value_sucks;
$sub->($file, @values);
[download]

Now, the dispatch table can be in a module, built on-the-fly, or whatever. What's happening here is that we're taking references to subroutines and associating them with strings. So, whenever we see a given string, we can map that to the given subroutine. This is very similar (but more powerful) to funcp's in C/C++.

------
We are the carpenters and bricklayers of the Information Age.

The idea is a little like C++ templates, except not quite so brain-meltingly complicated. -- TheDamian, Exegesis 6

Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.