The 'qx' keyword is just another way to write the back quote (`). The code -

$n = qx/ $got /;
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is equivalent to

$n = `$got`;
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What it does is to execute the $got command, and capture its output to a scalar.

You should have a look on CPAN perlop under the section "Quote and Quote-like Operators".

Update: Thanks to ysth to point out my typo.