I think that you have the procedural interface confused with the OO interface. Your code mixes the two. It seems that your intent was to use the procedural interface:

 use Net::SCP qw(scp); is procedural---not OO.

$scp = Net::SCP->new( "155.226.205.195", "metrica");
$scp->get("/apps/instl/metrica/sample.txt") or die $scp->{errstr};
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---is OO.

I would stick with procedural and take another look at the code that ysth posted.