#!/usr/bin/perl -w

use strict;

my $n=0;open(OUT,">$n.out");
while(<>) {
    print OUT or die "Lost file handle\n";
    if (/foo/) {close(OUT);$n++;open(OUT,">$n.out") or die "Can't
get file handle\n";}
}
print "Reached EOF\n";
close(OUT);