Any help would be appreciated.

The sooner you switch to pQuery, HTML::TreeBuilder::LibXML/HTML::TreeBuilder::XPath ... the better off you'll be

#!/usr/bin/perl --
use strict;
use warnings;

my $fafafa = <<'__FAFAFA__';
<iframe width="560" height="349" src="http://www.youtube.com/embed/8lG
+m40pxw" frameborder="0" allowfullscreen></iframe>
__FAFAFA__

print $fafafa;

$fafafa =~ s~<iframe([^>]+)>~'<iframe '.Fafafa("$1");~gie;

print $fafafa;
    
sub Fafafa {
    my %kava;
    my @bool;
    while( $_[0] =~ m{
        \G
        (?:
            ( [^'"\s=]+ )        # $1, key
            \s* = \s*
            " ( [^"]+)" # $2, val
        )
        |
        ( [^'"\s=]+ )           # single
        |
        \s
    }gxs
    ){
        no warnings 'uninitialized';
        print "1($1)2($2)3($3)\n";
        if( $3 ){
            push @bool, $3
        } elsif( $1 ) {
            $kava{$1}=$2;
        }
        
    }
    
    use DDS; Dump(\%kava);
    return join ' ', @bool, map { qq'$_="$kava{$_}"' } keys %kava;
}

__END__
[download]

<iframe width="560" height="349" src="http://www.youtube.com/embed/8lG
+m40pxw" frameborder="0" allowfullscreen></iframe>
1()2()3()
1(width)2(560)3()
1()2()3()
1(height)2(349)3()
1()2()3()
1(src)2(http://www.youtube.com/embed/8lGm40pxw)3()
1()2()3()
1(frameborder)2(0)3()
1()2()3()
1()2()3(allowfullscreen)
$HASH1 = {
           frameborder
                  => 0,
           height => 349,
           src    => 'http://www.youtube.com/embed/8lGm40pxw',
           width  => 560
         };
<iframe allowfullscreen width="560" frameborder="0" src="http://www.yo
+utube.com/embed/8lGm40pxw" height="349"</iframe>
[download]

I note you are matching against attribute="value" throughout and matching a single space between attribute/value pairs. The source HTML could easily contain additional whitespace such as attribute = "value".

If you're going to do the matching yourself (rather than using one of the tools like those shown above), you need to take this into consideration.

Shouldn't you be using the YouTube Mobile URLs? (They start with http://m.youtube.com.)