#!/bin/perl -w
use strict;

my %tmp;

while( my $tmp=<DATA>)
  { if( $tmp=~ /^(.+)(\d+)$/)
    { $tmp{$1}->[$2]= 'foo'; # don't you love auto-vivification?
    }
  }

__DATA__
foo2
foo5
foo0
bar
bar2
bar1
foo3