#! perl -slw
use strict;

our $N //= 1e6;

my $file1 = 'file1';
my $spill = 'temp';

open FILE2, '<', 'file2' or die $!;

my $done = 0;
until( $done ) {
    
    ## Index a batch of records from file 2
    my %idx;
    for( 1 .. $N ) {
        chomp( my @bits = split /\*/, <FILE2> );
        $idx{ $bits[ 0 ] } = $bits[ 1 ];
        $done = 1, last if eof FILE2;
    }
    
    open FILE1, '<', $file1 or die $!;
    open SPILL, '>', $spill or die $!;

    ## process records from file (or spill) file
    while( <FILE1> ) {
        chomp( my @bits = split /\*/ );
        
        ## If it exists in this batch, write the modified record to STDOUT
        if( exists $idx{ $bits[ 0 ] } ) {
            print join '*', $bits[ 0 ], $idx{ $bits[ 0 ] }, $bits[ 2 ];
        }
        else { ## otherwise put it in the spill file for next pass
            local $\;
            print SPILL;
        }
    }
    close SPILL;
    close FILE1;
    
    ## switch the input(file1) and spill file names
    ( $file1, $spill ) = ( $spill, $file1 ) unless $done;
}

## Anything left in the spill file goes through unmodified
local $\;
open SPILL, '<', $spill;
print while <SPILL>;
close SPILL;

## Remove the tempories
unlink $spill;
unlink $file1;