Since others have helped solve your problem, I thought I'd point out that the List::Util core module has a sum function equivalent to your calcsum function: 
use strict;
use warnings;
use List::Util qw(sum);
my @userArray = <STDIN>;
my $sum = sum(@userArray);
print "Sum $sum\n";

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In reply to Re: Use of uninitialized value in addition (+) by toolic
in thread Use of uninitialized value in addition (+) by Anonymous Monk

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