#!/usr/bin/perl
use strict;

# For debugging:
sub dump {
    my( $name, $ref ) = @_;
    require Data::Dumper;
    my $dumper = Data::Dumper->new( [$ref], [$name] );
    $dumper->Indent(1)->Useqq(1)->Terse(1);
    print STDERR $dumper->Dump();
}

my $foo = "Test value";
dump( foo => $foo );
# Should instead used:
#&dump( foo => $foo );
# ...
[download]

produces:

abnormal program termination
[download]

Helpful, isn't it? I suspect quite a few people don't immediately see what the problem is. I also suspect that no small number of people could waste quite a bit of time trying to figure this problem out before the solution comes to them and they snack themselves in the forehead.

Adding the & or renaming the sub to debugDump or moving the sub to a module will solve the problem.

The problem is that dump is a built-in. I don't care to memorize the entire list of Perl built-ins nor to put my code at risk when new built-ins are added (rarely).