#!/bin/sh -- # This comment tells perl not to loop!
eval 'exec /usr/bin/perl -S $0 ${1+"$@"}'
    if 0;

use English;
$OUTPUT_AUTOFLUSH = 1;		# Don't buffer stdout

#-----------------------------------------------------
# HABASH Sat Feb  7 16:11:54 EST 2004
# interleave.pl <file-A> <file-B> <pattern>
# <pattern> = (AABB|BBAA|ABAB|BABA)
#-----------------------------------------------------


$argc  = @ARGV;
if ($argc != 3) {die("Usage: $0 <file-A> <file-B> <pattern>\n   <pattern> = (AABB|BBAA|ABAB|BABA)\n");}

$fileA = $ARGV[0];
$fileB = $ARGV[1]; 
$pattern = $ARGV[2];

unless (open(A,$fileA)) {
    die ("Cannot open input file $fileA");
}
unless (open(B,$fileB)) {
    die ("Cannot open input file $fileB");
}
unless ($pattern=~/^(AABB|BBAA|ABAB|BABA)$/) {
    die ("Unrecognized Pattern $pattern");
}

@header=@footer=@A=@B=@combo=();

while ($line=<A>){
    if ($line=~/^\@/) {@header = (@header , $line)}
    if ($line=~/^\[/) {@A = (@A , $line)}
    if ($line=~/^\(/) {@footer = (@footer , $line)}
}
while ($line=<B>){
    if ($line=~/^\[/) {@B = (@B , $line)}
}

close(A);
close(B);

if ($pattern=~/^AABB/){
    @combo=(@A,@B);}
elsif ($pattern=~/^BBAA/){
    @combo=(@B,@A);}
else {
    for ($i=0;(($i<@A)||($i<@B));$i++){
	if ($pattern=~/^ABAB/){
	    @combo=(@combo, $A[$i] , $B[$i])}
	else { #pattern = BABA
	    @combo=(@combo, $B[$i] , $A[$i])}
    }
}

foreach $h (@header){
    print $h;
}
print "\n";
foreach $c (@combo){
    print $c;
}
foreach $f (@footer){
    print $f;
}