use IPC::Open2;

$file = $ARGV[0];

local *FRGZ;
local *TOGZ;
local *FRCMD;

$pid1 = open2(*FRGZ, *TOGZ, "gzip -dc $file");
$pid2 = open2(*FRCMD, '<FRGZ', 'mycommand');

while (<*FRCMD>)
{

    print;
}