I decided to abuse sprintf, just for fun. I imagine that substr and ikegami's regex solutions are significantly faster with real data. 

#!/usr/bin/perl
use strict;
use warnings;

my $max_len = 6;
for my $i (
    "  ab ", 
    "  ab   ", 
    "  abc   ", 
    "  abcd   ", 
    "  abcde   ", 
    "  abcdef   ", 
    "  abcdefg   "
) {
    my $o = abuse_sprintf($i);
    printf "%-15s%s", qq("$i"), qq( => "$o"\n);
}

sub abuse_sprintf {
    my $i = shift;
    
    length $i <= $max_len and return $i;

    my ( $a, $b, $c ) = $i =~ /\A(\s*)(.*?)(\s*)\z/s
        or die "bad input";
    
    length($b) >= $max_len
        and return sprintf "%.*s", $max_len, $b;
    
    length($a) + length($b) >= $max_len
        and return sprintf "%.*s%s", $max_len - length($b), $a, $b;

    return sprintf "%.*s", $max_len, $a . $b . $c;
}

[download]

In reply to Re: Truncate string to limited length, throwing away unimportant characters first. by rowdog
in thread Truncate string to limited length, throwing away unimportant characters first. by ambrus

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.