use strict;

my $line = "http://127.0.0.1/home_dir";

if ($line =~ /     # begin regex
         (         # begin Capture #1
         http:       # protocol
         )           # end Capture #1
         \/+          # (discard) one (or more) forward slashes; imprecise
         (127\.0\.0\.1)    # Capture #2, including the dots IP
         \/              # (discard) one forward slash
         (home_dir)       # Capture #3 (literal and simplistic)
         /x)           # end regex, use extended syntax, end the if predicate

      {
            print "$1\n";
            print "$2\n";
            print "$3\n";
            }
            else
            {
            print "Bad RegEx\n";
      }
exit;

##</code><code>##

http:
127.0.0.1
home_dir

##</code><code>##

use strict;

my $line = "http://127.0.0.1/home_dir";

if ($line =~ m%     # begin regex - alternate delimiter
         (          # begin Capture #1
         http:       # protocol
         )           # end Capture #1
         /{2,2}          # (discard) exactly two forward slashes
                         # note: no need to escape the "/" now,
                         # can also be written as {2} in some cases
         ([\d.]{1,14})   # Capture #2, including literal dots IP
         /               # (discard) one forward slash
         (\w{1,9})     # Capture #3, one-or-more (chars in range a-z OR underline)
         %x)           # end regex, use extended syntax, end the if predicate

      {
            print "$1\n";
            print "$2\n";
            print "$3\n";
            }
            else
            {
            print "Bad RegEx\n";
      }
exit;