In being tasked with modifying an ancient parser I soon noticed that it was using local $/=undef. Which I gathered is generally frowned upon.

It is not. It is frowned upon if it is used in a nonsensical way, like in the code snippet you posted.

Used at toplevel local has no effect, since there is no outer scope: you could just as well modify the global $/ instead. And if readline (or the diamond operator <>) isn't, but sysread used instead, setting $/ doesn't do anything useful.

sysread reads bytes. A subsequent chomp on the result only removes $/ (in your case: nothing, since $/ is undef) if $/ happens to be at the end of the resulting string - which will only be the case if your input file has fixed record length.

Instead of avoiding to use local $/ use it right - inside a BLOCK, so after leaving that block (at runtime) it gets its previous value:

{
    local $/; # undef by default if localized

    # file slurp here

}
# after the block, original $/ is restored
[download]

Try e.g. perl -le "{ local $/ = '@'; print ord $/,': ',$/ } print ord $/,': ',$/"

Result:

64: @
10:
[download]

Read up chomp. That line

    push(@records, chomp($record));
[download]

doesn't do what you expect. with $/ set to undef your array @records will contain only empty (undef) elements.

See also my/local, space/time (was: Re: The difference between my and local).