But what's the problem? Maybe you could provide an example of how your code is failing to deal with '/' properly. In the following example I decode your sample JSON, grab the key that looks like a regular expression, compile it as a regular expression, and use it to perform a match.

use strict;
use warnings;
use JSON;

use constant KEY   => 0;
use constant VALUE => 1;

my $json_string = <<'END_JSON';
{
  "regex" : {
    ".*/home/members/index.htm.*" : {
      "404" : {
        "reporting" : "1000",
        "paging" : "2000"
      }
    }
  }
}
END_JSON

my @test_strings  = qw( 
  web/home/members/index.htm?garbage=bye
  /home/memberzzzz/index.htm?garbage=bye
);

my $decoded_json = JSON->new->decode( $json_string );

# The regex is contained within a hash key.
my $regex_string = (%{$decoded_json->{regex}})[KEY]; 

my $regex        = qr/$regex_string/;

foreach my $test_string ( @test_strings ) {
  if( $test_string =~ m/$regex/ ) {
    print "Bingo! [$test_string] matches the pattern '$regex_string'\n
+";
  }
  else {
    print "Boo! [$test_string] doesn't match the pattern '$regex_strin
+g'\n";
  }
}
[download]

No special escaping of '/' here. The qr// operator is convenient.