I have an Entry widget where the textvariable is initialised as a numeric before the widget is created. The widget and validate routine looks like: 

my @c_speed = (5, 8, 12, 8);

my $cs_e1   = $seg1_f->Entry(-textvariable => \$c_speed[0], -width => 
+4,
                         -validate => 'all',
                         -vcmd     => \&validate_speed,
                         -font => $med_font)->grid(
                         -row => 0, -column => 1,
                         -sticky => "w");

sub validate_speed{
  my $val = shift;
  $val ||= 0;
  #get alphas and punctuation out
  if( $val !~ /^\d+$/ ){ return 0 }
  if (($val >= 0) and ($val <= 20)) {return 1}
    else{ return 0 }
}

[download]

To me this looks like $val is being treated as a string (if( $val !~ /^\d+$/ )) and then on the next line as a numeric variable ($val >= 0) etc. The code does what I want/expect but how? Is this just 'magic behind the curtain'?

In reply to Tk Entry widget confusion by colintu

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.