Just do your conversions in the -command sub. 
#!/usr/bin/perl
use warnings;
use strict;
use Tk;
use Tk::Spinbox;

#see also JComboBox

my $mw = MainWindow->new;
$mw->title("Spinner");

$mw->fontCreate('big',
        -family=>'courier',
        -weight=>'bold',
        -size=>int(-18*18/14));
       
my $dtm_unit = 'm';
my $dtm_old = 'm';       
my $sp1 = $mw->Spinbox(-width => 2, 
              -font => 'big',
              -textvariable=>\$dtm_unit,
              -command => sub{ &show_set },
          -value => ['m','cm','mm','in'])->pack (-side=>'left');


MainLoop;
###########################################################3

sub show_set{
   print "@_\n";


   print "$dtm_unit\n";

   print "old-> $dtm_old\n";

   $dtm_old = $dtm_unit;
}

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I'm not really a human, but I play one on earth. Cogito ergo sum a bum

In reply to Re: Previous Selection in Spinbox by zentara
in thread Previous Selection in Spinbox by shreedarasp

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