If you can use images for the creation of the text, then maybe you could use Image::Magick to draw the text and also find the dimensions of the text. 
$image->Read('How long am I');
($text_width) = $image->Get('width');

[download]
I found this information in "Programming Web Graphics" by Shawn P. Wallace (pg. 141) This is the only way I know of to find the pixel width of an object on a webpage.
Here is a quick script so you can try it out and see if it's what your looking for.
HTH 
use Image::Magick;

my $image = Image::Magick->new();

my $ps = 15;
$image->Set(pointsize=>$ps);
$image->Read("Label: Test ");
my $l = $image->Get('width');
print $l, "\n";

[download]

In reply to Re: Length of rendered TTF string in pixels? by steveAZ98
in thread Length of rendered TTF string in pixels? by Anonymous Monk

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.