#! /usr/bin/perl -w
@marks = (56, 23, 87, 79);

@diffs = diffsFromAvg(@marks);
$theAvg = diffsFromAvg(@marks);
print "List context: @diffs";
print "\nScalar Context: $theAvg";

sub diffsFromAvg
{
$numOfEls = @_;
$total = 0;
$total += $_ foreach (@_);
$avg = $total / $numOfEls

if (wantarray)
{
return map $avg - $_, @_;
}
else
{
$avg;
}
}