There's plenty of options. Maybe too many!

Regular expressions are one. For example - assuming your line has address, state & postcode: 
my ($addr,$state,$pc) = $line =~ /([^,]+),([^,]+),([^,]+)/;

[download]
Stick that in a loop as you iterate over your file: 
open DATA , "<", "path-to-file";
my @pcodes;
while (my $line = <DATA>){
my ($addr,$state,$pc) = $line =~ /([^,]+),([^,]+),([^,]+)/;

## Not a valid data line? Then move on.
defined $pc or next;

push @pcodes, $pc;
}
## Do stuff with @pcodes

close DATA;

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Now you can do what you like with the post codes. Note that this doesn't read the whole file in one go - but 1 line at time.
If memory is a problem you could pause every 10k records, or so, and print out to file.

Is that any use to you?

In reply to Re: Parsing/manipulating CSV files by mrstlee
in thread Parsing/manipulating CSV files by Ansi

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