-nE'@;{/./g}=();%;=!say%;'

/./g is in list context, so it's a shorthand for /(.)/g and will hence return a list of all characters (without the newline).

@;{...} is a slice of the hash %;. @;{/./g} = () sets all values in the slice to undef. The keys are the characters of the line.

say %; prints the hash; as key-value pairs. Since the values are undefined, the values are printed as empty strings. So, in effect, it prints all the characters of the line, without duplicates.

%;=!say%; say will return true, so its negation will be the empty string. So it'll make %; have one element: the empty string as key, and the undefined value as value. This will be printed for the next line, but since they are both printed as empty strings, you won't actually see it.

In reply to Re^3: Collapsing a string to unique characters by JavaFan
in thread Collapsing a string to unique characters by dwhite20899

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.