You did not test your code. The character matched by the dot is being lost in the replacement. The following snippet:

my $agent = 'PerlBeginnerPerl';
$agent =~ s/.([A-Z])/ $1/g;
print $agent;
[download]

produces: Per Beginne Perl

To make your approach work, you would need: $agent =~ s/(.)([A-Z])/$1 $2/g;