Overhead how? Depending on what I'm doing, hash-slicing might be harder to maintain than map. 
my %is_month_abbrev = map { $_ => undef } qw( 
    jan feb mar apr may jun jul aug sep oct nov dec
);

# versus ...

my %is_month_abbrev;
@is_month_abbrev{ qw( jan feb mar apr may jun jul aug sep oct nov dec 
+) } = (undef) x 12;

# or, with an intermediate array ...

my @months = qw( jan feb mar apr may jun jul aug sep oct nov dec );
my %is_month_abbrev;
@is_month_abbrev{@months} = (undef) x @months;

[download]
Often, losing a few micro-seconds is worth readability and maintainability. In both the slicing solutions, I either needed a separate array or hard-coding a magic number. (The number of months in a year isn't always a given. Some calendars have as few as 10, others have up to 14, and still others vary from year to year.)
My criteria for good software:
  1. Does it work?
  2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

In reply to Re^4: Unhappy returns by dragonchild
in thread Unhappy returns by tlm

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.