You want my @values = split /\./, $ip instead.

Dot "." is the "match-all" character in a regex so your split won't return anything.

Actually split returns a lot of things, it's just that the way list assignment works there is nothing left to put in the array.    If you make a slight change you can see everything that split returns:

$ perl -le'my $ip="158.21.17.45"; my @values = split(".", $ip, -1); pr
+int $ip,"\t\t",$#values,"\n";'
158.21.17.45            12
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Not sure what you mean about list assignment; the difference is that a third parameter of -1 makes split keep trailing empty strings where by default it discards them. In your example, split returns 13 empty strings (one from before the first character of $ip, one for each position between characters, and one from after the last character.)
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split's first argument isn't matched literally. It's treated as a regex pattern. The regex pattern can be provided as any of the following:

• a string,
• a compiled pattern
• a match operator (which passes a compiled pattern)

The following are equivalent:

my @octets = split('\\.',  $ip);
my @octets = split(qr/\./, $ip);
my @octets = split(/\./,   $ip);
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I always use the last syntax. It avoids confusion.

You might also be interested in Socket's inet_aton (and inet_ntoa).

(Note that split ' ' is special. See split's documentation if you're interested in details.)

use strict;
use warnings;

my $ip="158.21.17.45";
my @values = split(/\./, $ip); #<----Notice the Regex.

print $ip,"\t\t",$#values,"\n";

for my $val (@values){
        print "$val\n";
        }

exit(0);
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158.21.17.45        3
158
21
17
45
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