Can you post your exact code sample, please?

In the snippet you posted:

#all this works:
my $xmlsimple = XML::Simple->new();
my $response = $xmlsiple->XMLin($xml_content->content);
print "resultid:" . $response->{channel}->{result}->{resultid};
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there's clearly a typo; in one place you have $xmlsimple, and another $xmlsiple.  I'm guessing maybe the part that "doesn't work" might be the reverse -- a typo which you've inadvertently corrected when you posted.

Try actually cutting and pasting your code (and be sure to use "code tags" (eg. <code> and </code>) around any code examples you submit).

One other suggestion -- put use strict; and use warnings; at the beginning of your program.  That may even solve your problem right away!