If you have (or can install) PerlIO::gzip, you can read and write compressed files using an IO layer, like this: 
use PerlIO::gzip;

open( INPUT, "<:gzip", "old.gz" ) or die "old.gz: $!";
open( OUTPUT, ">:gzip", "new.gz" ) or die "new.gz: $!";

while (<INPUT>) {
    # do something with a line of text...
    s/[\r\n]+/\n/;  # for example, normalize line terminations
    print OUTPUT;
}

[download]
If for some reason you have constraints that get in the way of installing non-core modules, but you have "gzip" and "gunzip" on your system (and in your PATH), you can just use pipeline opens: 
open( INPUT, "gunzip < old.gz |" ) or die $!;
open( OUTPUT, "| gzip > new.gz" ) or die $!;
while (<INPUT>) {
    # same as above...
}

[download]
There are other methods as well, involving other modules (try looking at the search results for gzip at CPAN).

UPDATE: (2010-10-18) It seems that PerlIO::gzip should be viewed as superseded by PerlIO::via:gzip. (see PerlIO::gzip or PerlIO::via::gzip).

In reply to Re: reading compressed data by graff
in thread reading compressed data by kettle

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.