You're trying to call the method proxy() on the object $ua (with $ua->proxy('http', $prx)) before you've initialized the object.

You've conflated what should be two separate lines:

my $ua = ... ;      # constructor
$ua->proxy( ... ) ; # subsequent method call
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Also see the docs for my(), which is used to declare variables.

my $foo->bar('baz'); # will never compile
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Hope this helps!

OK, you've got me on the right track. Working but not pulling the proxy value from the file. Here's the modified code

open(my $fh, '<', 'cities.txt') or die $!;
    print $fh;
    open(my $prx, '<', 'proxies.txt') or die $!;
    print $prx;
    
    mkdir 'Bing', 0755;
    mkdir 'Bing/1Parsed/', 0755;
    mkdir 'Bing/1Parsed/Html/', 0755;
    
    chomp(my @cities = <$fh>);
    close($fh);
    
    chomp(my @prx = <$prx>);
    print $prx;
    close($prx);

    open($fh, '<', 'keywords.txt') or die $!;

    for my $city (@cities) {
        seek($fh, 0, 0);

        while (my $keywords = <$fh>) {
            chomp($keywords);
            print "$city $keywords\n";

    my $xml1 = $link1 . $city ."+". $keywords . $link2 . $city ."+". $
+keywords . $link3;
    #my $xmla = $link3 . $row . ".com";
    #my $xmlx = $link4 . $row;

    my $filename1 = "Bing/".($city)."_". ($keywords) . ".html";
    open my $fh1, ">", $filename1 or die("Could not open file. $!");
    
    #toggle proxy selection
    
    my $prx=$_;
    my $ua = LWP::UserAgent->new; 
    $ua->proxy(['http'], $prx);
    print $prx;
    $ua->agent('Mozilla/8.0');
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Your code does not compile (Missing brackets).

You are redefining "my $prx", which was previously a file handle.

You are assigning an un-initialized $_ to $prx.

Perhaps you meant it to look something like this:

my $ua = LWP::UserAgent->new; 
$ua->agent('Mozilla/8.0');

for my $p (@prx){
    print "Current proxy:$p\n";
    $ua->proxy(['http'], $p);
     # Use this UA/Proxy to fetch something....
}
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