The replies so far will work if you are trying to store the entire %ENV, but if you are just trying to create a subset of %ENV you can use the following (also generically for selecting hash subsets):

use strict;
use warnings;

# Stuff some matches into %ENV
# It's interesting to note in the output that the keys are uc'd
$ENV{SERVER_junk} = 'junk';
$ENV{SERVER_test} = 'test';
$ENV{ReQuEsT_job} = 'job';
$ENV{http_header} = 'header';
    
my @match = qw( server_ request_ http_ );
my %hash;

foreach my $key (keys %ENV) {
   print "$key => $ENV{$key}\n";
   foreach my $test (@match) {
      if ($key =~ /^$test/i) {
         $hash{$key} = $ENV{$key};
      }
   }
}

print "\nResults\n---------------------\n";
foreach (keys %hash) {
   print "$_ => $hash{$_}\n";
}
[download]

Resulting Output:

TEMP => C:\windows\TEMP
SERVER_TEST => test
REQUEST_JOB => job
SERVER_JUNK => junk
COMSPEC => C:\WINDOWS\COMMAND.COM
HTTP_HEADER => header
PATH => C:\PERL\BIN;C:\WINDOWS;C:\WINDOWS\COMMAND
WINDIR => C:\WINDOWS

Results
---------------------
SERVER_JUNK => junk
SERVER_TEST => test
HTTP_HEADER => header
REQUEST_JOB => job
[download]

--Jim