I quite often provide Perl apps compiled into executables with perl2exe for deployment on systems without Perl installed. As such I always provide a back-door means by which the configuration can be adjusted e.g.: -

use strict;
my $cake = 'chocolate';
my $pie = 'apple';
eval slurp("config.pl");
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Which will run config.pl at run time assuming a nice handy slurp function is provided to read a file...

## slurp - read a file into a scalar or list
sub slurp {
    my $file = shift;
    local *F;
    open F, "< $file" or die "Error opening '$file' for read: $!";
    if(not wantarray){
        local $/ = undef;
        my $string = <F>;
        close F;
        return $string;
    }
    local $/ = "";
    my @a = <F>;
    close F;
    return @a;
}
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So when config.pl contains...

$pie = 'pecan';
cake = 'fairy';
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...the pie and cake get set to your favourites rather than the defaults.

If you are interested in errors from the eval, it can be followed by something like...

if($@){
    print "Some errors happened...\n\n";
    print $@."\n\n";
    print "Oh well...\n";
}
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