#!/usr/bin/perl -w
use strict;
my $foo = "FOO";
my $bar = "BAR";
my $foobar = "FOOBAR";
sub foo {
    format STDOUT =
FOO      BAR
@<<<<<<< @<<<<<<<
$foo, $bar
.
    write;
}

sub foobar {
    format STDOUT =
FOOBAR BAR
@<<<<< @<<<<<<<
$foobar, $bar
.
    write;
}

foo() if ($ARGV[0] =~ /^foo$/i);
foobar() if ($ARGV[0] =~ /^foobar$/i);