For completeness sake ... this time using HTML::Parser:

use HTML::Parser;

$p = HTML::Parser->new( api_version => 3,
                             start_h => [\&start, "tagname, attr"],
                             end_h => [\&end, "tagname"],
                             marked_sections => 1,
                           );

{
    my $in_link = 0;
    sub start {
        my($tagname, $attr) = @_;
        if ($tagname eq 'a') {
            $in_link = 1;
        } elsif ($in_link and $tagname eq 'img' and exists $attr->{alt
+}) {
            print "IMG: $attr->{src} = $attr->{alt}\n";
        }
    }
    
    sub end {
        $in_link = 0 if ($_[0] eq 'a');
    }
}

$p->parse('sadf dsfg<a href="foo.html"><iMg src="foo.gif" alt="blah"><
+/a>
<img src="bar.gif" alt="nenene"> sdf');

$p->eof();
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