http://www.perlmonks.org?node_id=11160559

colintu has asked for the wisdom of the Perl Monks concerning the following question:

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'?

Back to Seekers of Perl Wisdom