Two common patterns:

my ($substr) = $var =~ /(pattern)/;
print $substr, "\n"
   if defined $substr;
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if ($var =~ /(pattern)/) {
   print "$1\n";
}
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Don't forget to put the parens around what you want to capture.

Update: Two common patterns for multiple matches:

my @substrs = $var =~ /(pattern)/g;
print "$_\n"
   foreach @substrs;
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while ($var =~ /(pattern)/g) {
   print "$1\n";
}
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Thanks for the responses, it worked like a charm.

To expand on ikegami's answer, take a look at Regexp::Common::net. It contains a pre-built regex pattern that recognizes dotted decimal IP addresses (constructing your own could be tricky). The example given in the synopsis section illustrates how it could be used. See also perlre for information about how to capture matches into variables.

would like to load into another variable $ip just the ip address which is contained within the variable $webpage

use NetAddr::IP::Find;

$content = "this is valid IP 202.155.22.3";
find_ipaddrs($content, sub {
             my ($a)= @_;
             print $a, "\n";
           });
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