# getting just the year
$y = (localtime($utc))[5]+1900;

# Basic hash un-rolling 
# (this is an example, better var names in real life)
foreach my $a (sort keys %hash) {
    foreach my $b (sort keys %{ $hash{$a} }) {
        # co-workers stumble at the line above
    }
}

# in an OO module
sub print_stats {
    $_[0]->{fh}->stats();
}

# lastly, co-workers are often confussed by :
use strict;

##</code><code>##

$ perl -e 'do() || ! do() ;'
Undefined subroutine &main::try