I believe you would use Term::Cap to find the terminal's width. In some systems, it may be directly available as an environment variable (COLUMNS)

You would then determine the length of your longest field (in your sample case, it would be the length of the string "Wednesday", plus 3 (for the colon and the two spaces that should follow a colon), plus 2 (for the length of '12' as a string), plus the padding you want between columns (you could use tabs, too). Figure out how many will fit (if you use tabs, which means you'll have to find out how wide a tab is in your output terminal. It's usually, but not always, 8). Build a format for sprintf or printf, and loop through the hash until finished. The lengths can be determined while the hash is being built. To force left-justification of a string, use something like "%-10s".