Hi jinnicky,

Although I'm no Tk expert, I investigated the AM's hint about dual-valued variables, and there indeed seems to be something buggy going on. I boiled the code down to the following:

use warnings;
use strict;
use Tk;
use Devel::Peek;

my $scale = '22.5 '; # note the space in the output as well
my $foo = 0 + $scale; # use in numeric context (set NV and IV)
Dump($scale);

my $mw = MainWindow->new;
$mw->Entry(-textvariable=>\$scale)->pack;
$mw->bind("<Key-Return>",\&calc);
calc();
MainLoop;

sub calc {
    print "str: <$scale> / num: <".(0+$scale)."> \n";
}

[download]

Output:

SV = PVNV(0x1e3f350) at 0x1e59a40
  REFCNT = 2
  FLAGS = (NOK,POK,IsCOW,pIOK,pNOK,pPOK)
  IV = 22
  NV = 22.5
  PV = 0x1e6f870 "22.5 "\0
  CUR = 5
  LEN = 10
  COW_REFCNT = 1
str: <22.5 > / num: <22>

[download]

It appears that binding $scale to the Tk::Entry widget is causing the variable to become dual-valued with the wrong initial values (I guess the PV and IV values?). This only seems to be happening once on init though, when I input something everything seems to work fine. I don't know enough about the internals of Tk to really suggest a solution (perhaps a bug report is in order), but some workaround(s). You apparently can initialize $scale with a numeric value to begin with, my $scale = 22.5; seems to work for me. Or, as you've already discovered, you can stringify $scale when reading it out.

Hope this helps,
-- Hauke D

In reply to Re: Perl is ignoring fractional part sometimes by haukex
in thread Perl is ignoring fractional part sometimes by jinnicky

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