There is a difference in how readline() handles references to typeglobs from 5.00503 and 5.6.1. The following works in 5.6.1:

#!/usr/bin/perl -w
use strict;
use Symbol;

my $sym = gensym;
open($sym, 'file1') || die "Can't $!";
while(readline($sym)){
    print;
}
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But it doesn't work in 5.00503 (no warnings, readline simply returns undef so the loop isn't entered). Reading from <$sym> works in both version when $sym is a globref, but readline() itself didn't work with globrefs until 5.6 --- I didn't see mention of it in perldelta, but it is mentioned in the 'Changes' file for 5.6 sources:

_________________________________________________________________
[  3349] By: gsar                         on 1999/05/09  20:23:07
        Log: allow readline($globref), <$globref> already works
     Branch: perl
           ! pp_hot.c
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A work around for 5.005 is to simply dereference the globref explicitly for the readline() function. The following work in 5.00503 and 5.6.1:

    readline(${$sym})
    readline(*{$sym})

or in your particular case:

    readline(*{$data[$i]->{FH}})
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As a final note, in your last block where you pad out the string I think you want to substract the expand()'d length, not just the length():

# change this:
print $_, ' 'x($data[$i]->{w}-1-length);

# to this:
print $_, ' 'x($data[$i]->{w}-1-length(expand($_)));
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